ANYL Sem Abstracts
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This page contains the abstracts for upcoming and past Analytical & Environmental Chemistry Seminars at CU. Please post newer seminars at the top, but do not erase the abstracts from old seminars.
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Monday, April 18, 2016
Effects of Atmospheric Conditions on the Composition of Secondary Organic Aerosol Formed from the Oxidation of Isoprene and Monoterpenes
Department of Chemistry and Biochemistry
University of Colorado, Boulder
Motivated by the Southern Oxidant and Aerosol Study (SOAS) field campaign of 2013, a series of environmental chamber experiments have been conducted to study the effect of environmental conditions on aerosol composition formed from biogenic VOC precursors. The experiments, performed under conditions that mimic those observed during SOAS, study the secondary organic aerosol (SOA) formed from the oxidation of isoprene and select monoterpenes. The composition of the SOA formed was characterized using spectrophotometric functional group analysis methods to quantify the amount of carbonyl [C(O)], carboxylic acid [C(O)OH], hydroxyl [CHOH], ester [C(O)OR], peroxide [CHOOR] and nitrate [CHONO2] groups in the aerosol. Further molecular analysis was done on select systems using various mass spectrometry methods. By comparing the composition of the chamber aerosol with field samples collected during the SOAS campaign, we will attempt to identify the chemistry that leads to aerosol formation in the southeast US.
Monday, April 11, 2016
On the Lifetime of Nitrogen Oxides in the Continental Boundary Layer
Ronald C. Cohen
Miller Professor 2015-2016
Professor, Department of Chemistry
Professor, Department of Earth and Planetary Science
University of California, Berkeley
Nitrogen oxides drive the chemistry of the troposphere, catalyzing production of oxidants, ozone and aerosol. Textbooks describe this chemistry as starting with emission of NO and terminating with the gas phase reaction of OH with NO2 to produce HNO3. Here, I will describe approaches to observing and characterizing the lifetime of nitrogen oxides using in situ and space based observations. In contrast to the textbook story we find the lifetime of nitrogen oxides on the continents are primarily controlled by organic nitrate formation.
Monday, April 4, 2016
Heterogeneous Efflorescence by Mineral Dust Particles
Department of Chemistry and Biochemistry
University of Colorado, Boulder
One of the key factors that determines particle growth and heterogeneous reaction efficiency of aerosols is whether the particle is liquid or solid. Salt aerosols transition between these phases through efflorescence and deliquescence. Although homogeneous efflorescence has been studied in detail, heterogeneous efflorescence is not well understood. Here we examined heterogeneous efflorescence by optically levitating single droplets of salt solutions and exposed the droplet to a flow of mineral dust particles. The impact of mineral dust on efflorescence and the difference between immersion and contact efflorescence will be discussed.
Monday, March 28, 2016
Chemistry of Multifunctional Hydroperoxides in Secondary Organic Aerosol
Department of Chemistry and Biochemistry
University of Colorado, Boulder
Multifunctional hydroperoxides have been identified as a product of autoxidation reactions and have been proposed as structures for extremely low volatility compounds (ELVOCs) observed in secondary organic aerosol. The chemistry of these hydroperoxides is complex and challenging to study, as many conventional analytical techniques disturb the peroxide functionality and cause additional chemistry to occur. In this work we are able to produce multifunctional hydroperoxides in environmental chamber reactions as well as in solution, allowing us to investigate their chemistry under a variety of conditions. Observed intramolecular reactions, reactions with water, acid-catalyzed acetal formation and acid-catalyzed peroxyacetal formation are all discussed.
Monday, March 14, 2016
The Seasonality of Tropospheric Ozone and Reactive Nitrogen: From Measurements to Models
Erin E. McDuffie et al.
Department of Chemistry and Biochemistry
University of Colorado Boulder
Tropospheric ozone is a potent greenhouse gas that forms through the oxidation of volatile organic compounds (VOCs) in the presence of nitrogen oxides (NOx). Previous field studies have largely focused on summertime ozone photochemistry that varies non-linearly with NOx and VOCs. First I will present results from OH reactivity, ozone production efficiency, and box-model analyses that quantify the impacts of regional oil and natural gas (O&NG) emissions on photochemical ozone in the Northern Front Range (NFR) of Colorado. The NFR is unique in that it has been non-compliant with ozone air quality standards since 2007 and has ozone precursor emissions from urban-Denver in close proximity to a rapidly developing O&NG basin. Second I will present an initial analysis of winter field data and discuss planned work aimed at addressing scientific uncertainties in wintertime O3 proces
Monday, March 7, 2016
Effect of a Functional Group on SOA Yields and Particle Composition from OH Radical Initiated Reactions of Alkanes in the Presence of NOx
Department of Chemistry and Biochemistry
University of Colorado Boulder
In a series of laboratory experiments we have identified major products and determined SOA yields from the reactions of C10 alcohol and C12 ketone position-isomers with OH radicals in the presence of NOx. Reactions were studied with a particle beam mass spectrometer (PBMS), gas chromatograph with flame ionization detection (GC-FID), and a scanning mobility particle sizer (SMPS), among other instruments. Functional group position had a considerable effect on SOA yields, which is fully explainable by the fate of alkoxy radical intermediates and vapor pressures of resulting products. Important observed differences from alkane chemistry were enhanced decomposition via α-cleavage, ability of the preexisting ketone to play a role in cyclic hemiacetal formation, and significantly hindered isomerization when the ketone was part of the transition-state ring.
Monday, February 29, 2016
Supercooling and ice formation of perchlorate and chloride brines under Mars-relevant conditions
Department of Chemistry and Biochemistry-CIRES
University of Colorado Boulder
Perchlorate and chloride salts, discovered in the Martian regolith at multiple landing sites, may provide pathways for liquid water stability on current Mars. It has previously been assumed that perchlorate and chloride brines form in the Martian regolith via melting or deliquescence, they would be present only briefly because efflorescence into a crystal or freezing to ice would soon occur. Here, we used a Raman microscope to study the temperature and relative humidity (RH) conditions at which magnesium perchlorate and magnesium chloride brines will deliquesce into aqueous droplets, form ice, and effloresce back into crystalline particles.
Monday, February 22, 2016 -- IN THE CIRES AUDITORIUM
Investigating hydrocarbon emissions in oil and gas basins using mobile platforms
Deparmtment of Chemistry and Biochemistry
University of Colorado
Methane emissions are of concern due to methane’s contribution to global climate change and tropospheric ozone formation. Sources of methane include landfills, agriculture, and oil and natural gas operations. Recent studies have focused on determining the extent to which oil and gas operations contribute to methane emissions. The National Oceanic and Atmospheric Administration’s (NOAA) Global Monitoring Division has conducted fieldwork in oil and gas basins in order to characterize and quantify emissions of methane and non-methane hydrocarbons. Field campaigns from the past two years will be presented. Measurement techniques and methods, including the use of a mobile laboratory and aircraft, will be discussed.
Monday, February 15, 2016
Chemistry in of the coldest places in the atmosphere: Impacts of updated NOx lifetime and fate on lightning NOx emission rates
Benjamin A. Nault
Department of Chemistry and CIRES
University of Colorado, Boulder
Nitrogen oxides (NOx ≡ NO + NO2) produced from lightning are an important natural source of NOx. This is the most important NOx source for the middle and upper troposphere. Lightning produced NOx controls the chemical production of middle and upper tropospheric ozone, an important greenhouse gas, and the oxidative capacity of the troposphere. However, the uncertainty in the emissions rates range from 2 to 8 Tg nitrogen per year. Recent studies have provided evidence that the oxidation of NOx to pernitric acid and nitric acid is slower than currently assumed and that methyl peroxy nitrate is an important temporary sink of upper tropospheric lightning NOx. Also, the conversion of dinitrogen pentoxide to nitric acid may be slower than currently assumed. I investigate the impacts of this updated kinetics and chemistry on model and in-situ observations of lightning NOx production rates. I show that using these results, the uncertainty range decreases. Also, the emission rates for different regions of the world increase by as much as 33% with the updated upper tropospheric NOx lifetime and fate.
Insights into Submicron Aerosol Composition and Sources from the WINTER Aircraft Campaign over the Eastern US
Department of Chemistry and CIRES
University of Colorado, Boulder
The WINTER aircraft campaign was a recent field experiment to probe the sources and evolution of gas and aerosol pollutants in Northeast US urban and industrial plumes during the winter. A highly customized Aerodyne aerosol mass spectrometer was flown on the NCAR C-130 to characterize submicron aerosol composition and evolution. Work towards constraining wintertime secondary organic aerosol formation and evolution will be presented from a case study of urban outflow from NYC. Observations and results of wintertime aerosol nitrate, power plant plume acidity, as well as measurements made from an oxidation flow reactor, flown for the first time, will be discussed.
Monday, February 1, 2016
Measurement of volatile organic compounds in the atmosphere using NO+ chemical ionization mass spectrometry
Abigail Koss, C. Warneke, P. Veres, B. Yuan, M. Coggon, J.A. de Gouw
Department of Chemistry and Biochemistry
University of Colorado, Boulder
The underutilized technique of NO+ chemical ionization mass spectrometry (NO+ CIMS) may improve volatile organic compound (VOC) measurement in the troposphere. In this talk I describe the development of an NO+ CIMS instrument and evaluate the usefulness of the NO+ technique. The evaluation is established through labwork using a gas-chromatography (GC) interface, in-situ measurement of urban air using a GC interface, and direct measurement of urban air. NO+ is useful for fast (1Hz) measurement of carbonyl isomers, for small aliphatics, and large (C13-C15) n-alkanes. The NO+ CIMS technique may be an extremely useful approach for studies of SOA formation, photochemistry, and emissions from fossil fuels and biomass burning.
Monday, December 7, 2015
Parameterization and evaluation of airborne halogen oxide measurements in the tropical transition layer and lower stratosphere
Barbara Dix, Sr. Research Associate
group of Prof. Rainer Volkamer
Dep. of Chemistry and Biochemistry
University of Colorado, Boulder
Tropospheric halogen oxides catalytically destroy ozone, modify oxidative capacity and oxidize atmospheric mercury. Ozone is an important precursor for OH, which determines the lifetime of methane, an important greenhouse gas. About 75% of the global tropospheric ozone and methane loss occurs at tropical latitudes, where further the ozone radiative forcing is most sensitive to changes in the ozone budget. We have measured bromine and iodine monoxide (BrO and IO) by Airborne Multi-Axis Differential Optical Absorption Spectroscopy (AMAX-DOAS) over the Western, Central and Eastern tropical Pacific Ocean. AMAX-DOAS measures solar scattered light along changing lines of sight to detect trace gases at different altitudes. Light path lengths at instrument altitude can reach up to a few hundred km in thin air, which enables detection limits of about 0.3 pptv for BrO and 0.05 pptv for IO for 60s and 30s integration time respectively. The initial result of a DOAS analysis is the integrated concentration along the line of sight, i.e. a column measurement. To derive volume mixing ratios from MAX-DOAS data typically involves the time consuming process of simulating the light path contributions to each measured spectrum by radiative transfer modeling. Here we present a method to parameterize radiative transfer, which allows for a fast conversion of column measurements into volume mixing ratios along the flight track. We will compare parameterized results with vertical profiles we retrieved by inversion techniques and discuss advantages and limitations of our new method.
Monday, November 30, 2015
Immediate fates of the world’s oldest pesticide in California’s most lucrative crop
Eve-Lyn S. Hinckley
Assistant Professor of Environmental Studies
Fellow of the Institute of Arctic and Alpine Research
Elemental sulfur (S0) has been used as an effective pesticide in agricultural systems since ancient Egyptian civilization. Today, in California’s winegrowing regions, applications of S0 dust are used as a preventative against powdery mildew infestation. Throughout the growing season, average applications are 150 kg S ha-1 yr1, and over Napa Valley vineyards alone, the applications total 810 Mg S0. Based on decades of research in northeastern U.S. forests that documented devastating ecosystem consequences of inadvertent reactive S and nitrogen deposition, I was inspired to understand how intensive, widespread, purposeful additions of S0 affect local-to-regional scale soil and water quality in agricultural systems. In Napa Valley vineyards, I have explored (1) What are the immediate fates of S0 locally in soils? and (2) What are the unintended consequences of its intensive, widespread use for downgradient ecosystems? In this talk, I will show the connection between hydrologic controls and the fate of S0 in California vineyards, and discuss how the pattern and consequences of continued applications might change under current drought conditions in the State. Ultimately, decisions about S pesticide management and water use in California’s winegrowing regions have implications for the sustainability of this industry, as well as the function of surrounding terrestrial and aquatic ecosystems.
Monday, November 16, 2015
Light-absorbing impurities and spectral albedo of the Juneau Icefield
Jennifer Lynne Berry
Department of Chemistry and Biochemistry
University of Colorado, Boulder
Light absorption by ice is extremely low in the visible and near ultraviolet wavelengths, so small concentrations of light-absorbing impurities can have a large effect on snow and ice albedo. Snow samples containing light-absorbing impurities were collected alongside measurements of spectral albedo on the Juneau Icefield in Alaska to investigate this effect. An Integrating Sphere/Integrating Sandwich Spectrophotometer (ISSW) was constructed to infer black carbon and non-black carbon light-absorbing particle concentrations in snow. Although calibration of the ISSW is incomplete, Nanoparticle Tracking Analysis and SEM-EDX images of particles from meltwater show a wide range of particle sizes and distribution across the icefield.
Chemical and Physical Alterations of Acid-Treated Aluminosilicate Clay Minerals and Impacts on Heterogeneous Ice Nucleation
Department of Chemistry and Biochemistry
University of Colorado, Boulder
Mineral dust aerosol is a major contributor to global ice nucleation, although atmospheric processing of mineral dust by sulfuric and nitric acids has been found to alter its ice nucleation ability. Samples of kaolinite and montmorillonite, two aluminosilicate clay minerals, were treated with aqueous sulfuric and nitric acid to simulate atmospheric processing. The samples were studied X-ray diffraction, transmission electron microscopy, and inductively coupled plasma–atomic emission spectroscopy were used to study the structural changes due to acid treatment, which were correlated to observations found in ice nucleation experiments. On the basis of lattice spacing arguments, the observed reduction in ice nucleation activity of acid-treated minerals were correlated to physical and chemical alterations to the mineral structure and the formation aqueous salts on the mineral surface.
Monday, November 9, 2015
The Genetics of Terpenoid Production in Cannabis
Ecology and Evolutionary Biology
University of Colorado at Boulder
The Cannabaceae family produces an astonishing diversity of cannabinoids and related terpenes, which are thought to collectively provide the complex flavor and aroma of hops, as well as the psychoactive and medical effects of Cannabis. New research provides important insights into the genetic variation underlying this phytochemical diversity, and sheds light on approaches that can be used to improve breeding efforts to up- or down-regulate the production of these compounds.
Monday, November 2, 2015
Diversity of bioaerosols in indoor and outdoor air across the U.S.
Ecology and Evolutionary Biology
and Fellow of CIRES
University of Colorado at Boulder
Every time we breathe we are inhaling thousands of bacterial cells, fungal cells, and pollen grains. Although most of these microbes are innocuous, it is well-established that some airborne bacteria, fungi, and pollen can have important effects on human health. However, we have a limited understanding of how these bioaerosols vary across different geographic regions or the factors that structure their biogeographical patterns. We conducted a citizen science project that involved collecting dust samples from inside and outside ~1,500 households located across the U.S. to understand the continental-scale distributions of bacteria and fungi in indoor and outdoor air. We used high-throughput DNA sequencing to assess the diversity and sources of these bioaerosols, yielding our first insight into the continental-scale distributions of bioaerosols and how they are influenced by climate, land-use, home occupants, and home design.
Size-Dependent Molecular-Level Characterization of Secondary Organic Aerosol from NO3 Initiated Δ-carene Oxidation using Nanospray Desorption Electrospray Ionization High-Resolution Mass Spectrometry
Department of Chemistry and Biochemistry
We have collected size-separated Δ-carene oxidation aerosol samples using a Micro-orifice Uniform Deposit Impactor (MOUDI) by injecting Δ-carene into a dark flow-through chamber under low RH conditions (< 30%) with O3 and NO2 so the dominant reaction pathway would be with NO3 to form highly oxidized products.
The samples were analysed with a Nanospray Desorption Electrospray Ionization (nano-DESI) high-resolution mass spectrometer in both the positive and negative modes to reveal that the faster growing, and thus larger diameter, branch had a higher oxygen-to-carbon (O:C) ratio when compared with the lower branch, suggesting that the faster growing branch is more oxidized. Furthermore, the most intense peaks from the two branches were compositionally different, but a significant proportion of the formulas identified had N:C ratios of ~0.1, which suggests that organic nitrates are a large component of the aerosol products.
Monday, October 26, 2015
High-resolution mass spectrometry: peak fitting and aerosol partitioning
Department of Chemistry and Biochemistry
University of Colorado, Boulder
When measuring oxidized organic molecules in the atmosphere, often thousands of compounds can be present and provide a challenge for conclusive assignment in high-resolution mass spectra, particularly when the goal is to retrieve data series over long time periods of weeks or months, as typical in field campaigns. We have developed algorithms to identify and assign peaks in complex mass spectra to produce reliable peak lists for analyzing large data sets. Simulation of mass spectra confirmed the validity of the assignment algorithms for calculation of bulk chemical properties such as carbon number and carbon oxidation state. A new method of deriving such chemical properties without the need for any peak assignment will also be presented.
Application of a peak list from the new algorithms to measurements from a chemical-ionization mass spectrometer deployed in a Pine forest in Colorado allowed measurement of gas-particle partitioning of hundreds of organic compounds. Comparing two methods of deriving saturation concentration distributions (“volatility basis sets”) from the same dataset highlights the importance of fragmentation in thermal desorption techniques.
Particle Size Resolution of the Aerodyne Aerosol Mass Spectrometer
Department of Chemistry and Biochemistry
University of Colorado, Boulder
Real-time determination of chemically-resolved particles size distributions and their evolution in laboratory and ambient studies can be used to investigate changing source contributions, growth rates, secondary aerosol yields, cloud condensation nuclei potential and other physicochemical processes. The Aerodyne Aerosol Mass Spectrometers (AMSs) provides fast size and chemical composition measurements of particles from ~50 nanometers to ~1 micrometer. This work addresses the resolution of the size measurement via particle time-of-flight (PToF) in this instrument. An algebraic model is used to estimate size resolution for different configurations of the instrument as well as particle diameters and vaporization rates. Under typical AMS configurations, for a given particle size, resolution is primarily controlled by the uncertainties in particle time-of-flight due to the finite opening time of the particle gating chopper and particle vaporization. The model was tested with a range of chopper gate widths, particle sizes, and particle compositions, and agreements and disagreements are investigated. The methodology to estimate the size resolution can be applied to all instruments that use particle time-of-flight to infer particle size. Instrument and data acquisition configurations can be optimized for a range of different particle sampling conditions including ambient sampling under low or high loadings, for aircraft platforms, for laboratory applications where loadings may be controllable or narrow particle size ranges are present, and when single-particle chemical or light-scattering detection is possible.
Monday, October 19, 2015
Portable Air Pollution Monitors and the Global Ozone (GO3) Project
President, 2B Technologies and Director, Global Ozone (GO3) Project, Boulder, CO
Over the past 15 years we have developed highly portable instruments for measurements of ozone, NO, NO2 and black carbon. These instruments have enabled measurements in remote locations and extreme environments around the world. Our small, light-weight, low-power instruments have been widely used for atmospheric measurements on balloons, kites, UAVs, towers, trams and research aircraft, and at many remote sites, including Antarctica, the Galapagos Islands, the Greenland ice sheet, the summit of Mont Blanc, the Amazon rain forest, on buoys in the Arctic Ocean, on commercial airliners, in many U.S. National Parks and at numerous other locations throughout the world.
The Global Ozone or “GO3” Project was founded as a non-profit organization for educational outreach in 2009. In the GO3 Project, middle and high school students at more than 100 schools around the world measure air pollutants and meteorological parameters outside their schools and upload their data to a public database every 15 minutes. The data may be graphed online and displayed on Google Earth. Students interpret their results and discuss their findings in blogs and forums in a social network similar to Facebook. The GO3 Project includes an online, interactive curriculum where students learn about atmospheric environmental problems and how they are interrelated, including: ground level ozone, stratospheric ozone depletion ("ozone hole"), acid rain and global climate change. The GO3 Project also includes a hands-on Black Carbon Experiment where students measure this important air pollutant by collecting particles on a filter and measuring the optical transmission through the filter using a simple but accurate photometer. In our newest project, GO3 Treks, students hypothesize how air pollutants vary along treks of their own design, and then carry out the treks using pocket-sized ozone and black carbon monitors. Treks are displayed on Google Earth within blogs where students discuss
Monday, October 12, 2015
CE-DOAS at its Detection Limit
1st Year Graduate Student
Cavity Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS) is an established method for the in-situ measurement of trace gas concentrations. Its detection limit is often not determined by noise but systematical effects.
I comment on the combined effect of high frequency intensity variations and the non-linearity of the spectrometer in intensity space on the detection limit, which is estimated from model calculations. I also present the new calibration method ICOM (Integrated Calibration by means of Optical Modulation) for the determination of light path lengths in optical resonators, which is promising because of its high performance concerning spectral resolution, absolute accuracy and precision.
Heterogeneous Chemistry in the tropical free troposphere
Professor of Chemistry and Biochemistry & CIRES Fellow, University of Colorado, Boulder
Tropospheric halogens catalytically destroy ozone, oxidize atmospheric mercury, and modify the oxidative capacity of the atmosphere. Ozone is a potent greenhouse gas, and an important precursor for hydroxyl (OH) radicals that determine the lifetime of CH4 another important greenhouse gas. About 75% of the global tropospheric O3 and CH4 loss occurs at tropical latitudes, where O3 radiative forcing is further most sensitive to changes in O3. Oxygenated VOCs (OVOC) affect the atmospheric oxidative capacity, modify NOx, and O3, but recent first measurements of selected OVOC, like glyoxal, methylvinylketone, and butanal in the tropical free troposphere currently remain unexplained by atmospheric models. Water soluble OVOC are further a globally relevant source of secondary organic aerosol (SOA). This talk reviews recent advances in instrumentation, and their applications in field observations, laboratory experiments, and modeling results in the Volkamer group. Selected recent publications: Waxman et al. (2015): Glyoxal and Methyl Glyoxal Setschenow Salting Constants in Sulfate, Nitrate and Chloride Solutions: Measurements and Gibbs Energies. Environ. Sci. Technol., doi: 10.1021/acs.est.5b02782. Saiz-Lopez et al. (2015): Injection of iodine to the stratosphere, Geophys. Res. Lett., doi: 10.1002/2015GL064796. Wang et al. (2015): Active and Widespread Halogen Chemistry in the Tropical and Subtropical Free Troposphere, Proc. Natl. Acad. Sci., 112 (30), 9281–9286, 2015. doi: 10.1073/pnas.1505142112. Volkamer et al. (2015): Aircraft measurements of BrO, IO, glyoxal, NO2, H2O, O2-O2 and aerosol extinction profiles in the tropics: Comparison with aircraft-/ship-based in situ and lidar measurements, Atmos. Meas. Tech. 8, 2121-2148, 2015. doi:10.5194/amt-8-2121-2015.
Monday, October 5, 2015
Building molecular complexity with sunlight at aqueous interfaces
Professor, Department of Chemistry and Biochemistry &
CIRES Fellow, University of Colorado-Boulder
High energy, low entropy solar radiation can be used to initiate radical reactions leading to organic polymers and oligomers in environmental systems. In atmospheric chemistry, the role of the photochemically generated OH radical is well studied. However, the role of other radicals, especially those generated from organic precursors, is less well-understood. This presentation will discuss examples of photochemically-initiated organic radical reactions at the water surface. Specifically, the photochemistry of oxoacids, such as pyruvic acid as well as a series of oxoacids with longer aliphatic side chains, will be discussed. Photochemical processing occurs with solar simulators under both aerobic and anaerobic environments, characteristic of the contemporary and ancient Earth’s atmosphere, respectively. The polymers produced are investigated by mass spectrometry and NMR, while the supramolecular aggregates that spontaneously self-assemble during photolysis are monitored by microscopy and dynamic light scattering. Implications of these abiotic processes to atmospheric and environmental chemistry will be discussed, specifically as they affect aerosol nucleation and growth.
Atmospheric Reduced Nitrogen: Trends and Future Directions
Professor of Chemistry and Biochemistry &
CIRES Fellow, University of Colorado, Boulder
Organic nitrogen is a ubiquitous atmospheric component typically accounting for between one-quarter and one-third of reactive nitrogen deposition, however, its chemical complexity and its reactivity has made it challenging to study. Consequently, little is known about the atmospheric processing of organic nitrogen and the resulting implications for biogeochemistry, air quality, and climate. Organic nitrogen can be broadly separated into two groups: oxidized organic nitrogen compounds such as acyl peroxy nitrates and reduced organic nitrogen compounds such as amines. Historically, our knowledge of the chemistry of reduced organic nitrogen has lagged behind that of oxidized organic nitrogen due to the dominance of oxidized nitrogen sources. Recent enactment of air quality regulations in the United States and parts of Europe, however, has resulted in decreased emissions of oxidized nitrogen while emissions of reduced nitrogen have remained constant or have increased due to expansion of agriculture and increased use of fertilizer. Thus, it is timely to study the chemistry of reduced organic nitrogen. I will discuss trends in emissions of reduced nitrogen, its implications for reduced organic nitrogen, and future studies on the chemistry of reduced organic nitrogen.
Monday, September 21, 2015
Chemistry of Organic Compounds in the Atmosphere and Indoor Air
Professor, Department of Chemistry and Biochemistry &
CIRES Fellow, University of Colorado-Boulder
Laboratory studies provide much of the fundamental data on reaction kinetics, products, and mechanisms that are needed to achieve a deep understanding of atmospheric and indoor air chemistry and to develop detailed and accurate models that are used to establish air quality regulations and to predict the effects of human activities. Research in my laboratory focuses primarily on the atmospheric chemistry of organic compounds emitted from natural and anthropogenic sources and the physical and chemical processes by which oxidized organic reaction products form microscopic aerosol particles. Studies are conducted in large-volume environmental chambers where experiments are designed to simulate but simplify atmospheric chemistry and conditions in order to obtain information on gas and particle chemical composition, reaction rates and equilibria, and particle properties. Obtaining such data is a challenge, but in this talk I will describe how we approach this problem by using a diverse array of measurement techniques. I will also discuss our more recent studies on the chemistry of indoor air.
Professor of Chemistry and Biochemistry &
CIRES Fellow, University of Colorado, Boulder
Title and Abstract Forthcoming<b>
Monday, April 13, 2015
<b>Optical properties of brown carbon aerosol in the near-ultraviolet spectral region
NOAA Chemical Sciences Division
Aerosol scattering and absorption are among the largest uncertainties in radiative forcing. Black carbon is a strong radiative forcing agent, and absorbs strongly throughout the ultraviolet and visible spectral regions. In contrast, brown carbon has a wavelength-dependent absorption that increases sharply in the ultraviolet spectral region and its importance in radiative forcing is more unknown. Part of this uncertainty arises from the need to characterize potential sources of brown carbon aerosol, which include fossil fuel combustion, biomass burning, and secondary organic aerosol aging processes.
We have developed a new method to measure aerosol optical extinction as a function of wavelength for in situ aerosol, using cavity enhanced spectroscopy. We have demonstrated this method over the 360-420 nm spectral region, and plan to extend it to 300 nm. We retrieve complex refractive indices as a function of wavelength from the measured extinction cross sections. In the laboratory, this technique has allowed us to examine a proposed mechanism to produce brown carbon aerosol from the reaction of ammonia or amino acids with carbonyl products in secondary organic aerosol.
During the Southern Oxidant and Aerosol Study in summer 2013, we acquired field measurements of aerosol optical extinction at 360-420 nm. We combined these data with direct absorption measurements of water-soluble organic carbon obtained from a UV/VIS-WSOC instrument, and with aerosol composition measurements. I will present the magnitude of brown and black carbon absorption and the relative contributions of biomass burning, anthropogenic, and secondary organic aerosol contributions to brown carbon absorption in the Southeast U.S. during the summer.
Monday, April 6, 2015
Forensics, Metabolomics and Molecular Imaging by Mass Spectrometry
Facundo M. Fernández, Ph. D.
School of Chemistry and Biochemistry
Georgia Institute of Technology
Mass Spectrometry (MS) is one of the key analytical methods used to identify and characterize small quantities of biological molecules embedded in complex matrices. Although MS has found widespread use, technical improvements in its instrumentation are needed to extend its application to the grand challenges that face the environmental, chemical and biomedical sciences. In this talk I will present insights into new approaches for generating ions under atmospheric pressure in an “open air” format followed by mass spectrometric detection. That research has enabled our group to perform a series of experiments in the fields of forensics, imaging and metabolomics. I will describe how “open air” MS has helped us detect the components in and track the sources of counterfeit drugs in developing countries, perform high throughput metabolic fingerprinting of patients with cancer, and image a variety of surfaces. I will also describe more fundamental work involving finite element simulations and Schlieren imaging of ion transport processes at the atmospheric pressure interface of the mass spectrometer. Finally, I will describe new results where plasma ion sources are used for better coupling of LC to MS.
Monday, March 30, 2015
Advances in the Quantitation of Atmospheric Organosulfates
Department of Chemistry
University of Iowa
Iowa City, IA 52242
Organosulfates are significant components of secondary organic aerosols (SOA) formed under acidic conditions. This class of compounds contains a characteristic sulfate ester functional group (R-O-SO3-) and is suggested to be a significant contributor to organic carbon in fine particles in the atmosphere. However, the quantification of individual organosulfates molecules has proven challenging due to the lack of authentic quantification standards and suitable methods of analysis. To overcome these challenges, a series of organosulfates standards was synthesized and used to develop and validate of a new analytical method for their quantification. Recent results from the application of this method to ambient aerosol collected in Centreville, Alabama during the Southeast Atmosphere Study (SAS) in 2013 will be discussed.
Monday, March 16, 2015
Tropospheric Reactive Chlorine: Observations, Sources and Effects
Lea Hildebrandt Ruiz, Ph.D.
The University of Texas at Austin
Cockrell School of Engineering
McKetta Department of Chemical Engineering
Austin, TX 78712-1589
Ambient measurements have detected tropospheric reactive chlorine concentrations much higher than predicted by state-of-the-art air quality models, challenging current understanding of the emissions and atmospheric chemistry of chlorinated compounds. For example, measurements in the Dallas Fort Worth (DFW) area routinely observed HCl concentrations of 1 ppb or more, peaking in the late afternoon. Modeling work has investigated several hypotheses for the source of HCl in DFW, and results suggest emissions of an organic chloride, potentially from hydraulic fracturing activity, as the most likely explanation. In the presence of particulate chloride reactive chlorine can also be formed from heterogeneous reactions on the particles’ surface. Laboratory chamber experiments were conducted to quantify the rate of heterogeneous production of chlorine, and results suggest that this path could explain observed sources of Cl2. Higher concentrations of reactive chlorine can lead to increased production secondary organic aerosol (SOA). Mass yields of SOA formed from chlorine-radical-initiated oxidation of hydrocarbons were measured in laboratory chamber experiments. Volatility basis set parameters from these experiments can be incorporated in air quality models to more accurately represent reactive chlorine concentrations and its effects on atmospheric composition.
Monday, March 9, 2015
Secondary Organic Aerosol Modeling using the Statistical Oxidation Model
Colorado State University
Multi-generational gas-phase oxidation of organic vapors can influence the abundance, composition and properties of organic particulate matter or organic aerosol. Most air quality and climate models lack or include an ad hoc treatment of multi-generational oxidation. In this seminar, I will highlight our recent work where we coupled a semi-explicit multi-generational oxidation model for organics (fully constrained by experimental smog chamber data that includes both functionalization and fragmentation reactions) with a gas-phase chemical mechanism in a regional 3-D air quality model. The seminar will discuss results where we (a) investigated the role of multi-generational gas-phase chemistry on the mass, composition, volatility and oxidation state of SOA and (b) explored the influence of vapor wall-losses on ambient concentrations and properties of SOA. Based on those results, I will argue that 3-D models need to include (this or similar) multi-generational oxidation schemes to accurately describe the atmospheric evolution of OA in air quality and climate models.
Monday, March 2, 2015
Optical Properties of Titan Haze Analogs Using Photoacoustic and Cavity Ring-Down Spectroscopy
Melissa S. Ugelow
3rd Year Graduate Student
The organic haze that surrounds Saturn's moon Titan is formed through the photolysis and electron initiated dissociation of methane and nitrogen. Both the chemical pathways leading to the haze formation and the resulting haze optical properties are still highly uncertain. Here we examine the optical properties of simulated haze aerosol to better understand its scattering and absorption properties, and the impact of haze on Titan's radiative balance. To determine the complex refractive index of haze particles, we combine two spectroscopic techniques, one that measures absorption and one that measures extinction: photoacoustic spectroscopy coupled with cavity ring-down spectroscopy (PASCaRD). This technique provides the benefit of a high precision determination of the imaginary component of the refractive index (k), along with the highly sensitive determination of the real component of the refractive index (n) in a flow system set up. The Titan aerosol analogs studied are produced by two energy sources, UV excitation and spark discharge excitation. The refractive indices are determined at two wavelengths, 405 and 532 nm, using the PASCaRD system. I will present preliminary data on the complex refractive indices of laboratory generated Titan aerosol analogs at both wavelengths using both energy sources. The high precision values determined from this method should be useful for modelers and for data retrieval from spacecraft and remote sensing instruments.
Monday, February 23, 2015
Chemical Nucleation in the Atmosphere: Recent Discoveries Enabled by Instrument Development
Peter H. McMurry
Department of Mechanical Engineering
111 Church St. SE
University of Minnesota, Minneapolis, MN 55455 USA
Observations throughout the atmosphere have shown that nucleation from the gas phase occurs every few days and that nucleation rates are correlated with collision rates of sulfuric acid vapor molecules. Our research team, which includes the groups led by Drs. Fred Eisele, Jim Smith and David Hanson, have developed three new instruments to study atmospheric nucleation: the Cluster Chemical Ionization Mass Spectrometer (Cluster CIMS), for measuring the concentrations of neutral molecular clusters formed by nucleation (1-10 ppqv sensitivity); the DEG Scanning Mobility Particle Spectrometer (DEG SMPS), for measuring the number distributions of freshly nucleated particles as small as 1 nm; and the Ambient Pressure Proton Transfer Mass Spectrometer (AmPMS), for measuring concentrations of basic organic and inorganic gases that react with and stabilize sulfuric acid-containing clusters (1pptv sensitivity).
Together, these instruments allow measurements of precursor vapor concentrations and the complete particle number distribution down to 1 molecule. This information is providing us with a new understanding of the physical and chemical processes that lead to nucleation.
Atmospheric observations and laboratory studies have confirmed that nucleation occurs due to a sequence of acid-base reactions that form stable clusters that subsequently grow by the further uptake of organic and inorganic compounds. Evaporation of sulfuric acid from clusters that contain 1 to 3 sulfuric acid molecules is the primary bottleneck to nucleation. Our measurements have provided estimates of these evaporation rates, leading to a simple analytic expression for nucleation rates that is in reasonable agreement with observations.
The seminar will describe the bases for these conclusions.
Monday, February 16, 2015
Rethinking Secondary Organic Aerosol formation and removal in 3D models based on explicit chemistry
Dr. Alma Hodzic, NCAR, Boulder, CO
Current secondary organic aerosol (SOA) parameterizations fail to explain the observed amounts and properties of tropospheric SOA, which results in large uncertainties in their effects on radiation and climate. We use the Generator of Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) to simulate SOA gas-phase chemistry in various environments (urban, forest, low/high NOx). Our results show that GECKO-A predicts significant SOA mass growth in urban plumes, and formation of less volatile and more soluble organic products, than predicted by parameterizations typically used in 3D models. The results also indicate that atmospheric processing of gas-phase oxidation intermediates, which are poorly represented in 3D models, can significantly modulate SOA formation and lifetime. We discuss the possible effect of dry deposition and organic photo-fragmentation reactions on condensable organic vapors and SOA. We derive new parameterizations that reproduce GECKO-A behavior in terms of volatility, yields and solubility for use in 3D models. These parameterizations are applied at regional and global scales to re-evaluate SOA concentrations, burden and removal.
Wednesday, February 11, 2015
Isoprene aerosol yields quantified with space-based relationships between aerosol optical depth and formaldehyde: contrasting regimes in Africa and the southeast US
E. A. Marais et al., Harvard University
Abstract: Isoprene is an important precursor of organic aerosol (OA), but yields of OA are uncertain. We obtain satellite-derived yields of isoprene OA for Africa and the southeast US by exploiting spatial and temporal consistency between aerosol optical depth (AOD) from MODIS and formaldehyde, ΩHCHO, from OMI. GEOS-Chem chemical transport model yields of isoprene OA using reversible partitioning of isoprene OA are low (<1%) and the resultant AOD is lower than MODIS AOD. GEOS-Chem shows the observed slope from regression of AOD against ΩHCHO is a sensitive indicator of yields of isoprene OA and reproduces observed slopes when partitioning to the aerosol phase is irreversible and regional mean isoprene OA yields are 5.5±1.8% for Africa and 8.6±2.4% for the southeast US. Gas-phase isoprene oxidation is predominantly by NO in the southeast US, and mixed NO and HO2 in Africa. Higher satellite-derived yields under NO dominant conditions is consistent with higher yields observed with chambers operating close to ambient NO2 to NO ratios. We infer lower yields of isoprene OA (3.0%) with boundary-layer southeast US SEAC4RS aircraft observations, as GEOS-Chem calculation of AOD is sensitive to vertical distribution of isoprene OA. Simulated yields of isoprene OA are uniform in GEOS-Chem, but SEAC4RS-derived yields increase to 4.2% at 2-4 km. The AOD we simulate in Africa and the southeast US with our satellite-derived yields implies larger direct radiative forcing from isoprene OA than previous model estimates.
Monday, February 9, 2015
Formation of Low Volatility Compounds and SOA from Isoprene Oxidation without IEPOX uptake
3rd Year Graduate Student
Department of Chemistry and Biochemistry
University of Colorado, Boulder
Many of the sources and formation mechanisms of secondary organic aerosol (SOA) are still poorly understood. In this talk, I will present evidence of gas-phase low volatility organic compounds (LVOC), produced from the OH oxidation of isoprene hydroxy hydroperoxide (ISOPOOH), condensing and forming secondary organic aerosol (SOA) during the Caltech FIXCIT chamber study. Decreases in LVOC concentrations directly corresponded to the appearance and growth in organic aerosol, indicating that LVOC were condensing and forming SOA (at OA levels below 1 μg m-3) with a wall-loss corrected mass yield of roughly 1.5% (from isoprene). This previously uncharacterized formation pathway from isoprene could account for up to 8.0 Tg yr-1 of SOA, or 5% of the estimated global SOA source. The experimental conditions and AMS SOA spectrum indicate that SOA formation in this study is separate and not explained by previously described IEPOX uptake. Condensing species have 4-5 carbons and volatilities consistent with multiple hydroxyl groups, as well as carbonyl and possibly hydroperoxide groups. These species are not extremely low volatility VOCs (ELVOC) as previously observed from monoterpene oxidation by O3, but most likely LVOC with saturation concentrations ranging from 10-2 to 10¬ μg m-3. Their ability to condense at low OA levels at room temperature and to grow nanoparticles indicate that their importance may be largest in environments with lower OA concentrations. The same LVOC compounds were observed in the atmosphere during the SOAS campaign in the SE US. The results of efforts to extract mechanistic information from an ion mobility spectrometer-mass spectrometer (IMS-MS) during the SOAS field study and subsequent laboratory work will also be presented.
Monday, February 2, 2015
Photon and Water Mediated Sulfur Chemistry in Planetary Atmospheres
Jay Kroll, 3rd Year Graduate Student
Department of Chemistry and Biochemistry
Sulfur compounds have been observed in the atmospheres of a number of planetary bodies in our solar system including Earth and Venus. The global cloud cover on Venus located at an altitude between 50 and 80 kilometers is composed primarily of sulfuric acid (H2SO4) and water. Planetary photochemical models have attempted to explain observations of sulfuric acid and sulfur oxides with significant discrepancies remaining between models and observation. I will report on recent laboratory studies attempting to measure the kinetics of reactions of SO2 and water to form sulfurous acid and progress made in instrument development.
Monday, January 26, 2015
Weeding Out the Myths: Introduction to Medical Marijuana
Laura Borgelt, FCCP, BCPS
Associate Dean for Administration and Operations
Professor, Departments of Clinical Pharmacy and Family Medicine
University of Colorado , Skaggs School of Pharmacy and Pharmaceutical Sciences
Medical marijuana laws and funded studies in Colorado make it increasingly important to understand the characteristics and appropriate use of medical marijuana. This presentation will use an evidence-based approach to introduce the endocannabinoid system and the pharmacology of marijuana as a potential treatment for various conditions. The proposed mechanisms of action for marijuana provide valuable information about its potential benefits and risks. Additionally, the pharmacokinetics of marijuana, including its absorption, distribution, metabolism, and elimination, will be discussed to help participants determine how various dosage forms may be used. The overall goal is to help participants learn more about how marijuana works and how that relates to the risks and benefits of using medical marijuana.
Monday, Nov. 17th, 2014
Iodine Monoxide observations from CU AMAX-DOAS aboard the NSF NCAR GV research aircraft
Theodore Koenig 3rd Year Graduate Student Department of Chemistry and Biochemistry, University of Colorado
The CU Airborne Multi-AXis Differential Optical Absorption Spectroscopy (CU AMAX-DOAS) instrument was deployed for the TORERO and CONTRAST field campaigns. These were in the Tropical Eastern Pacific in January-February 2012, and the Tropical Western Pacific in January-February 2014 respectively. We report the first scattered light limb measurements of IO. I will discuss a number of highlights from our observations: 1) instances of enhanced IO mixing ratios in the transition layer 2) a free troposphere background of IO that shows little variation with altitude 3) a hemispheric gradient in total IO column and 4) the first quantification of IO in the lower stratosphere. These measurements provide the best constraints to date on IO outside the planetary boundary layer. They offer the chance to begin assessing our understanding on iodine chemistry in the transition layer, free troposphere, and lower stratosphere and its impacts of climate, particularly tropospheric ozone.
Monday, Nov. 10th, 2014
ANALYTICAL & ENVIRONMENTAL CHEMISTRY DIVISION and ATMOSPHERIC CHEMISTRY PROGRAM SEMINAR
Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program
November 10, 2014 12:00 Noon - 1:00 pm Ekeley S274
University of Colorado, Boulder
Characterization of a Real-Time Tracer for Isoprene Epoxydiols-Derived Secondary Organic Aerosol (IEPOX-SOA) from Aerosol Mass Spectrometer Measurements
Weiwei Hu et al.
Cooperative Institute for Research in Environmental Sciences, and Department of Chemistry and Biochemistry, University of Colorado, Boulder
Secondary organic aerosol (SOA) can be formed from isoprene epoxydiols (IEPOX), compounds that are produced from isoprene oxidation under low-NO conditions. IEPOX-SOA can account for a substantial fraction of organic aerosol (OA) in biogenic-influenced areas. In this study, IEPOX-SOA was identified from measurements at the forested Southeast U.S. supersite (Centreville, AL) during the Southern Oxidant and Aerosol Study (SOAS) using Positive Matrix Factorization (PMF) of aerosol mass spectrometer (AMS) measurements. The SOAS results clearly show that the fraction of OA measured at C5H6O+ (fC5H6O) in AMS spectra is a good tracer for IEPOX-SOA and correlates with the well-known methyltetrol tracers of this chemistry. Other field and chamber studies are included in the analysis to investigate the robustness of fC5H6O as an IEPOX-SOA tracer in AMS data. We observed clearly higher fC5H6O (3x10-3 - 25x10-3) in OA from regions with strong isoprene emissions vs those from urban and biomass-burning plumes (0 - 3.5x10-3 with an average of 1.75x10-3). In isoprene-influenced areas, fC5H6O in ambient OA positively correlates with the relative contribution of IEPOX-SOA to OA and decreases with OA aging. The kOH for destruction of IEPOX-SOA via heterogeneous oxidation in aerosol phase is approximately 5.3x10-13 cm3 molec－1 s－1, with life time is around 14.5 days (assuming average OH concentration=1.5x106 molecular cm-3). Volatility analysis using a thermal denuder shows that IEPOX-SOA is not more volatile than bulk SOA, contrasting with the high volatility of the tracers identified. Finally, we develop a simplified method to estimate ambient IEPOX-SOA mass concentrations as a function of fC5H6O, which is shown to perform well compared to the full PMF method. When only unit mass resolution data is available as in ACSM data, the method performs less well because of increased interferences from other ions at m/z 82. Estimated IEPOX-SOA concentrations in the southeastern U.S. from an aircraft campaign (SEAC4RS)correlate well with the IEPOX-related species detected by other techniques over a wide range of conditions, which confirms the usefulness of our method. IEPOX-SOA accounts for 14 - 17% of the OA in the SE U.S. during the summer according to both the SEAC4RS and SOAS results.
Oxidation flow reactors for the study of atmospheric chemistry systematically examined by modeling
Zhe Peng Cooperative Institute for Research in Environmental Sciences, and Department of Chemistry and Biochemistry, University of Colorado, Boulder
Oxidation flow reactors (OFRs) using OH produced from low-pressure Hg lamps at 254 nm(OFR254) or both 185 and 254 nm (OFR185) are commonly used in atmospheric chemistry and other fields. OFR254 requires the addition of externally formed O3 since OH is formed from O3 photolysis, while OFR185 does not since O3 is formed in the reactor and OH can also be formed from H2O photolysis. In this study, we use a plug-flow kinetic model to investigate OFR properties under a very wide range of conditions applicable to both field and laboratory studies. We show that the radical chemistry in OFRs can be characterized as a function of UV light intensity, H2O concentration, and total external OH reactivity (e.g., from VOCs, NOx, and SO2). In OFR185, OH exposure is more sensitive to external OH reactivity than in OFR254, because injected O3 in OFR254 promotes the recycling of HO2 to OH, making external perturbations to theradical chemistry less significant. There has been some speculation in the literature about whether “non-tropospheric chemistry” (photolysis at 185 or 254 nm, and/or reactions with O(1D) and O(3P)) may play an important role in these OFRs. For field studies in forested regions or the urban area of Los Angeles, reactants of atmospheric interest are predominantly consumed by OH. Nontropospheric oxidants contribute to the degradation of some species under conditions of low H2O concentration and/or very high external OH reactivity. This appears to have been a problem in some laboratory and source studies, but can be avoided in future studies by experimental planning based on our findings. Some biogenic VOCs can have substantial contributions of reaction with O3 under some operating conditions, especially for OFR254. NO3 may have played an unexpectedly significant role in some past laboratory studies. RO2 fate is similar to that in the atmosphere under low-NOx conditions. A comparison of OFRs with typical environmental chamber studies using UV blacklights and with the atmosphere is presented. OFRs’ key advantages are their short experimental time scales, portability to field sites, enabling a direct connection of field and laboratory studies, and controllable and predictable radical chemistry. This study further establishes the usefulness of these reactors and enables better experiment planning and interpretation.
Monday, Nov. 3rd, 2014
Uncovering the structure and dynamics of a single nanoparticle using the world’s shortest laser pulses
Dan Hickstein, Kapteyn-Murnane Group, JILA, University of Colorado
Modern femtosecond lasers can produce pulses of light that are shorter than the vibrational periods in molecules and generate electric fields stronger than the Coulomb field that binds electrons in atoms. These lasers are ideally suited to studying ultrafast processes in nanomaterials, such as electron transfer in photovoltaic nanostructures. However, all previous laser-nanoparticle experiments have been conducted on nanoparticles suspended in solvent, embedded in a bulk material, or attached to a surface, meaning that powerful gas-phase spectroscopy techniques cannot be used. In 2011 we embarked on a collaboration with the Jimenez group to construct a photoelectron–photoion spectrometer capable of examining isolated nanoparticles in the “gas phase.” To our surprise, the completed spectrometer was capable of recording the complete photoion distribution resulting from the interaction of a single nanoparticle with the femtosecond laser pulse. This breakthrough technique has allowed for the examination of localized light fields in nanostructures, the discovery of shock waves in nanoscale plasmas, and the observation of the evanescent wavefunction in quantum dots. In this talk I describe how we combined the tools of physical chemistry, laser physics, and atmospheric science to construct this new instrument, describe the discoveries to-date, and discuss our plans for future experiments, which include pushing the time-resolution towards the attosecond frontier.
Monday, October 27th, 2014
The Structure of Atmospheric Particles & Impacts on Atmospheric Chemistry and Climate
Miriam Freedman, Penn State University
The interactions of aerosol particles with light and clouds are determined in part by the structure of atmospheric particles, which is the focus of research in my laboratory. My talk will focus on molecular-level studies of surfaces relevant for cirrus (ice) cloud formation and the phase separation behavior of submicron aerosol particles composed of organic and inorganic components. Through these projects, I will demonstrate the importance of characterizing aerosol structure in determining aerosol physical and chemical properties relevant to atmospheric chemistry and climate.
Monday, October 20th, 2014
Analysis of arson fire debris by low temperature dynamic headspace adsorption porous layer open tubular columns
Megan Harries, First Year Graduate Student, University of Colorado, Boulder
We present results of the application of PLOT-cryoadsorption (PLOT-cryo) to the analysis of ignitable liquids in fire debris. We tested ignitable liquids, broadly divided into fuels and solvents, on three substrates: Douglas fir, oak plywood and Nylon carpet. We determined that PLOT-cryo allows the analyst to distinguish all of the ignitable liquids tested by use of a very rapid sampling protocol, and performs better (more recovered components, higher efficiency, lower elution solvent volumes) than a conventional purge and trap method. We also tested the effect of latency (the time period between applying the ignitable liquid and ignition), and we tested a variety of sampling times and a variety of PLOT capillary lengths. Reliable results can be obtained with sampling time periods as short as 3min, and on PLOT capillaries as short as 20cm. The variability of separate samples was also assessed, a study made possible by the high throughput nature of the PLOT-cryo method. We also determined that the method performs better than the conventional carbon strip method that is commonly used in fire debris analysis. Future work will center on improving the understanding of phase equilibria of complex mixtures and on the development of relevant equations of state.
Poly- and Per-Fluorinated Alkyl Substances in the Environment
Julia Bakker-Arkema, 1st Year Graduate Student, Department of Chemistry and Biochemistry
This talk will explore the research of Dr. Scott Mabury and his work on poly and perfluorinated alkyl substances, or PFAS, in the environment. I will examine the ways that PFAS are transported and transformed in different systems, specifically the atmosphere, soil and water, and biological systems.
Monday, October 13th, 2014
Ozonolysis of a polyunsaturated acid and its primary oxidation products
Zachary Fineway, First Year Graduate Student, University of Colorado, Boulder
Detection of glyoxal, the smallest α-dicarbonyl, in remote locations over the Pacific Ocean, has prompted research into its sources. Glyoxal is likely produced by oxidation of compounds within the sea surface microlayer. Reactions of linoleic acid, a polyunsaturated fatty acid found in the sea surface microlayer, and its primary gas phase oxidation products yielded glyoxal without an OH scavenger present. In the presence of an OH scavenger, glyoxal production is significantly reduced, and malondialdehyde, the smallest β-dicarbonyl, was detected. These findings elude to a mechanism of glyoxal formation, and a possible explanation of why malondialdehyde has not been detected in the atmosphere.
Pond Scum and Boiling Water: Water Chemistry at Yellowstone National Park
Randall Chiu, First Year Graduate Student, University of Colorado, Boulder
Since the mid-1990’s, the Nordstrom lab at the US Geological Survey National Research Program (USGS NRP) has sampled numerous hot springs and rivers in Yellowstone National Park (YNP). The data, collected at least annually, provide a unique record of the inorganic chemistry (including major cations and anions, trace metals, and unusual species such as polythionates) of the geothermal waters at YNP. The data are used by collaborators at various universities to supplement microbiology research and also by USGS researchers investigating the geochemistry of YNP. This talk will summarize some of the current research efforts at YNP, with emphasis on USGS work that has public health and safety implications.
Monday, October 6th, 2014
Nitrogen Oxides and Aerosols (NOaA): Some applications of cavity enhanced spectroscopy in atmospheric chemistry
Stephen S. Brown
Chemical Sciences Division, NOAA Earth System Research Lab Department of Chemistry and Biochemistry, University of Colorado
Nitrogen oxides (NOx) are emitted from both anthropogenic and natural processes and critically influence the oxidizing capacity of the atmosphere. Aerosols arise from a variety of sources and impact climate through their radiative effects and atmospheric chemistry through heterogeneous and multiphase reactions. Nitrogen oxides in particular undergo distinct heterogeneous reactions that link gas and aerosol phase chemistry. Both nitrogen oxides and aerosols are amenable to measurement by new, high sensitivity optical techniques known as cavity enhanced spectroscopy. I will survey some recent efforts and future projects toward development of this instrumentation, as well as several applications, including nighttime chemistry, wintertime photochemistry and aerosol optical properties.
Monday, September 29, 2014
A new mechanism for solid formation in the atmosphere: contact efflorescence
Margaret Tolbert Professor, Department of Chemistry and Biochemistry & CIRES Fellow, Univ. of Colorado-Boulder
The phase state of atmospheric particulate is an important factor in the magnitude of both the direct and indirect radiative effect of aerosols on climate. While the homogeneous phase transitions of deliquescence and efflorescence have been studied for decades, there is far less information available on heterogeneous efflorescence. Here we describe a new mechanism of possible atmospheric importance, contact efflorescence, a process that occurs when a supersaturated droplet comes in physical contact with a solid particle. A newly constructed optical trap is used to measure contact efflorescence for single levitated droplets exposed to single collisions. This talk will describe the experimental technique and present preliminary data for contact efflorescence.
Laboratory Studies of the Chemistry of Secondary Organic Aerosol Formation
Paul Ziemann Professor, Department of Chemistry and Biochemistry & CIRES Fellow, Univ. of Colorado-Boulder
In this talk I will describe for incoming graduate students the atmospheric chemistry research being conducted in my laboratory. Laboratory studies provide much of the fundamental data on reaction kinetics, products, and mechanisms that are needed to achieve a deep understanding of atmospheric chemistry and to develop detailed and accurate models that are used to establish air quality regulations and to predict the effects of human activities on global climate. Research in my laboratory focuses on the atmospheric chemistry of organic compounds emitted from natural and anthropogenic sources and the physical and chemical processes by which oxidized organic reaction products form microscopic aerosol particles. Studies are conducted in large-volume environmental chambers where experiments are designed to simulate but simplify atmospheric chemistry and conditions in order to obtain information on gas and particle chemical composition; gas and heterogeneous/multiphase reaction rates and equilibria; thermodynamic, hygroscopic, and phase properties of particles; and gas-particle-wall interactions. Obtaining such data is a challenge, but in this talk I will describe how we approach this problem by using a diverse array of measurement techniques including real-time and offline mass spectrometry, temperature-programmed thermal desorption, gas and liquid chromatography, NMR, spectrophotometry, and scanning mobility particle sizing. I will then provide examples of our use of these methods to develop quantitative chemical reaction mechanisms of organic gas and aerosol chemistry and models of SOA formation and particle properties such as hygroscopicity and describe some ongoing research projects.
Monday, September 22, 2014
Volatile Organic Compounds in the Atmosphere
Joost de Gouw
Dept. Chemistry & Biochemistry
Volatile organic compounds (VOCs) are released to the atmosphere from a large variety of sources both natural and man-made. In the atmosphere, VOCs are oxidized by different radicals on time scales of minutes to years. As a result of this chemistry, ozone and fine particles can be formed, which are two important air pollutants and which also play a role in the climate system. I will discuss ongoing research at the NOAA Earth System Research Laboratory that is aimed at quantifying the sources of VOCs, their chemical transformations, and the impact of these processes on air quality and climate. Also, new sources of energy lead to emissions of different VOCs, which is an emerging issue in our research.
Prof. Jose-Luis Jimenez
Dept. Chemistry & Biochemistry and CIRES, Univ. of Colorado-Boulder
Summary of Recent Results and Upcoming Projects to Investigate Organic Aerosol Sources, Properties, Processes, and Fate
Organic aerosols (OA) account for about 1/2 of the submicron particle mass in the atmosphere leading to important impacts on climate, human health, and other issues, but their sources, sinks, and evolution are poorly understood. OA is comprised of primary OA (POA, emitted in the particle phase) and secondary OA (SOA, formed by gas-to-particle conversion). In this talk I will present an overview and highlights of research on OA instrumentation, measurements, and modeling by our group over the last year, as well as of upcoming projects of potential interest to 1st year students. Ongoing projects include analysis of SOA formation and aging from field studies in urban areas (CalNex-LA), forests (BEACHON-RoMBAS, SOAS, GoAmazon) and over regional scales from aircraft (DC3 and SEAC4RS), including direct measurements of the SOA formation and photochemical evolution from ambient air using an oxidation flow reactor (OFR). We are modeling the oxidation chemistry in the OFR in detail, and under most conditions we can show that non-tropospheric chemical pathways (e.g. reactions with O1D or photolysis at 185 or 254 nm) are negligible. SOA formation in LA is consistent with other urban sites. SOA formation and aging in the OFR is remarkably consistent across sites, showing peak formation at ~2 days of equivalent oxidation and loss of mass at ~2 weeks of oxidation. The detection and aging of SOA formed from isoprene epoxides in the Southeast US with the high-resolution AMS is shown to be robust, resulting in a ~15% contribution to the OA budget in summer and a lifetime of ~2 weeks against gas-phase aging. Gas/particle partitioning is measured directly using a FIGAERO-CIMS, with consistent results with other instruments at the SOAS site. Finally, I will introduce future projects in our group, including an update on the new shared smog chamber facility in the Cristol building (for which testing will start in October), development and application of chemical ionization mass spectrometry to laboratory research on OA gas/particle partitioning and to SOA formation from terpenes and the NO3 radical, and a NASA pole-to-pole aircraft field campaign on aerosol composition.
Monday, September 15, 2014
Research Overview of the Joint Center for Artificial Photosynthesis (JCAP):
Development of Scalably Manufacturable Solar-Fuels Generators
Carl Koval, Director
JCAP was established in 2010 as one of the DOE’s Energy Innovation Hubs. JCAP’s mission is to build fully integrated solar-fuels generators that utilize earth-abundant semiconductors and catalysts for efficient conversion of water to O2 and H2 and for the reduction of CO2 to liquid fuels. JCAP prototypes are designed to enable separation of products and therefore require membranes and complex interfaces between various material components that will function under realistic operating conditions. JCAP’s long-term goal is to develop a commercially viable, solar-generation technology that simultaneously satisfies the following four criteria: high efficiency, multi-year stability, low module cost, and safe operation. JCAP’s approach to assembling complete artificial photosynthetic systems is to develop robust concepts for complete solar-fuels generators, then to break them down into essential assemblies of components, and finally to adapt or discover the materials needed to fabricate those assemblies. JCAP research bridges basic and applied sciences as well as engineering associated with prototype construction and consideration of scale-up challenges.
Monday, September 8, 2014
Reactive trace gases in tropospheric chemistry and climate
Rainer Volkamer -- Presentation given by Volkamer Group
Reactive trace gases and aerosols are relevant components of tropospheric chemistry and climate. Bromine and iodine oxide radicals, and oxygenated VOC species modify the HOx radical abundance, influence the reactive chemistry and lifetime of climate active gases (e.g., ozone, methane, dimethyl sulfide) and can trigger the atmospheric deposition of mercury to ecosystems. Reactive trace gases are also a source for secondary aerosol mass that modifies aerosol optical properties, and cloud interactions (Earth albedo). The Volkamer group develops innovative optical spectroscopic instruments (in-situ and remote sensing) to measure trace gases and aerosols, and applies these instruments to conduct field measurements from mobile platforms (vehicles, ships, aircraft) and laboratory measurements in simulation chambers and flowtubes. This talk will present examples of current graduate student projects in the Volkamer group (MAD-CAT, CONTRAST, and FRAPPE projects). Future student opportunities exist in relation with the analysis of data from ongoing field projects, as well as laboratory studies that use in-situ cavity enhanced absorption spectroscopy and mass spectrometry to investigate the role of Setschenow ‘salting-in’ for aerosol formation. Prof. Volkamer is currently on sabbatical in Europe, and is best reached by email.
Tuesday, August 26, 2014
Explicit Modelling of the Multiphase Oxidation of Organic Compounds
Prof. Bernard Aumont, LISA and Univ of Paris XII
Atmospheric oxidation of organic matter is a gradual process involving a myriad of gaseous intermediates usually denoted as secondary organic compounds (SOC). These intermediates are typically species bearing one or more functional groups, such as ketone, aldehyde, alcohol, nitrate or hydroperoxide moieties. Secondary organic compounds play a central role in the chemistry of the atmosphere, being directly involved in the HOx/NOx/Ox tropospheric budget, in the production of particulate matter via the formation low volatility organic compound and in cloud chemistry via the formation of water soluble organic compounds. Explicit chemical mechanisms aim to embody the current knowledge of the transformations occurring in the atmosphere during the oxidation of organic matter. These explicit mechanisms are therefore useful tools to explore the fate of organic matter during its tropospheric oxidation and examine how these organic chemical processes shape the composition and properties of the gaseous and the condensed phases. Nevertheless, the explicit mechanism describing the oxidation of hydrocarbons with backbones larger than few carbon atoms involves millions of SOC, far exceeding the size of chemical mechanisms that can be written manually. Data processing tools can however be designed to overcome these difficulties and automatically generate consistent and comprehensive chemical mechanisms on a systematic basis. The Generator for Explicit Chemistry and Kinetics of Organics in the Atmosphere (GECKO-A) has been developed for the automatic writing of explicit chemical schemes of organic species and their partitioning between the gas and condensed phases. GECKO-A can be viewed as an expert system that mimics the steps by which chemists might develop chemical schemes. GECKO-A generates chemical schemes according to a prescribed protocol assigning reaction pathways and kinetics data on the basis of experimental data and structure-activity relationships. In its current version, GECKO-A can generate the full atmospheric oxidation scheme for most linear, branched and cyclic precursors, including alkanes and alkenes up to C25. Recent assessments and applications of the GECKO-A modeling tool will be presented, with a focus given to studies devoted to examine SOA formation and ageing, SOC phase partitioning and multiphase oxidation processes.
Monday, May 19, 2014
Surface observations of VOCs over the temperate southern hemispheric oceans
Dr. Sarah Lawson
CSIRO MARINE AND ATMOSPHERIC RESEARCH
VOCs fuel tropospheric ozone production, are precursors to secondary aerosol and influence the oxidative capacity of the atmosphere. The ocean is potentially a source (and sink) of many climatically important VOCs such as isoprene, monoterpenes and glyoxal, yet there are very few measurements over the remote oceans, particularly in the Southern Hemisphere. We present surface observations of VOCs over a very biologically active region of the South West Pacific Ocean (43ºS) during the 2012 Surface Ocean Aerosol Production (SOAP) voyage, and observations over the Southern Ocean from the Cape Grim Baseline Station (41ºS). VOCs were measured insitu using Proton Transfer Reaction Mass Spectrometry (PTR-MS) and also collected on 2,4-DNPH cartridges and VOC adsorbent tubes for later analysis by HPLC and GC/MS at CSIRO, Aspendale. Non-negligible mixing ratios of isoprene, monoterpenes, glyoxal and methyl glyoxal were all observed over the remote ocean indicating an oceanic source of these species. Very high mixing ratios of DMS were observed over phytoplankton blooms during SOAP alongside elevated levels of methanethiol and dimethyl sulfone . The significance of these observations is discussed and observations are compared with those elsewhere in the remote marine boundary layer.
Monday, May 8, 2014
Development of optical spectroscopic instruments and application to field measurements of marine trace gases
University of Colorado, Boulder
Halogens (X = Cl, Br, I) and organic carbon are relevant to the oxidative capacity of the atmosphere, and linked to atmospheric sulfur and nitrogen cycles, modify aerosols, and oxidize atmospheric mercury. The atmospheric abundance of halogen radical species in the atmosphere is very low, but even concentrations of parts per trillion (1 ppt = 10-12 volume mixing ratio) or even parts per quadrillion (1 ppq = 10-15 volume mixing ratio) in the atmosphere are relevant for the bioaccumulation of the neurotoxin mercury in fish. Halogen radicals can be traced through measurements of halogen oxides (XO, where X = Cl, Br, I), that are ~1-10 times more abundant. However, measurements of halogen oxides are sparse, partly due to the lack of analytical techniques that enable their routine detection. Global models are unable to accurately reproduce the few measurements that are available. I have developed a research grade Multi-AXis Differential Optical Absorption Spectroscopy (MAX-DOAS) instrument to measure bromine monoxide (BrO) and iodine monoxide (IO) routinely in the troposphere. I present autonomous measurements of BrO and IO in Pensacola, Florida that maximize sensitivity towards the detection of BrO in the free troposphere (altitudes >2km) from ground. The derived profiles are then coupled to a box-model to assess the impact of these measurements on the oxidation of mercury in the atmosphere. The second part of my talk describes first measurements of glyoxal diurnal cycles and Eddy Covariance fluxes of glyoxal in the marine atmosphere. Glyoxal is the smallest alpha-dicarbonyl, and a useful tracer molecule for fast photochemistry of hydrocarbons over oceans. The unique physical and chemical properties of glyoxal (i.e., high Henry’s Law coefficient, H = 4.2x105 M atm-1, and short atmospheric lifetime of ~2 hrs) pose challenges to explain this soluble gas over the remote ocean, and recent measurements over the open ocean currently remain unexplained by models. In order to better understand the sources and sinks of this molecule in the marine atmosphere, a Fast Light-Emitting-Diode Cavity-Enhanced DOAS (Fast LED-CE-DOAS) instrument was modified to measure eddy covariance fluxes of glyoxal. These are the first measurements of EC fluxes of glyoxal, and only the 7th molecule for which the EC flux technique has been used from ships. Results from a first cruise deployment over the tropical Pacific Ocean (TORERO field campaign) are presented.
Monday, April 28, 2014
Gas/Particle Partitioning of Organic Acids: instrument development and field deployment
University of Colorado, Boulder
Organic acids are common atmospheric oxidation products and can help our understanding of those mechanisms. In particular their partitioning between the gas and particle phase can lead to a better understanding of their contribution to SOA loadings and lifetime. In this talk I will be presenting the development a new instrument (the FIGAERO-HRToF-CIMS) for real time detection of both gas and particle phase organic acids. Results from lab characterization and a field campaign as part of the Southern Oxidant and Aerosol Study (SOAS) will be shown
Monday, April 21, 2014
Can Mass Spectrometry be More Radical?
Professor Yu Xia
Assistant Professor, Analytical Chemistry
Radical induced damage to biomolecules is highly relevant to aging, neurodegenerative diseases, and cancers. Fundamental understanding of radical-biomolecule interactions is important for the development of new drugs and therapeutic procedures, but is often missing. We have taken a unique approach to address this issue by studying gas-phase ion/radical reactions. Instrumentation and methods have been developed to enable ion/radical reactions in an electrospray ionization (ESI) plume or inside a linear ion trap mass spectrometer. Accurate mass measurement, stable isotope labeling, tandem mass spectrometry, and theoretical calculations are utilized to provide insight into the reaction mechanisms.
Monday, April 14, 2014
Chemical Reactions Among Pollutants Indoors – The Human Touch
Charles J. Weschler
Regardless of whether a pollutant originates outdoors or indoors, most of our exposure to it occurs indoors. Indoor exposures to ozone and airborne particles of outdoor origin partially explain the mortality ascribed to these pollutants in epidemiological studies. The human body influences indoor concentrations of these and other chemicals in occupied indoor environments. Constituents of human skin oil react with ozone. Lower indoor ozone concentrations lead to less generation of secondary organic aerosols (SOA) from ozone-initiated reactions with terpenes and other unsaturated indoor pollutants. SOA levels influence the levels of co-occurring semivolatile organic compounds (SVOCs). Occupants also inadvertently transfer their skin oils and skin flakes to surfaces, impacting indoor surface chemistry, even when humans are no longer present. In brief, dynamic physical and chemical processes involving occupants and indoor pollutants markedly influence occupant exposures in indoor environments.
Monday, April 3, 2014
Novel phase transitions of optically levitated microdroplets: Contacts and glasses relevant to the atmosphere
University of Colorado, Boulder
The phase state and water content of atmospheric particles influence the particle’s size, optical properties and chemical reactivity with important but poorly constrained effects on air quality and climate. One challenging problem is predicting the ambient conditions required to initiate a phase transformation of a particle from liquid to solid, particularly when consideration is given to multi-particle interactions as well as chemical composition of the liquid droplet. One such example is the phenomenon of contact nucleation. Presented here are the first direct observations of contact nucleation of crystalline ammonium sulfate using a recently developed long-working distance optical trap. Insight is given to the mechanism behind contact nucleation. The effect of amorphous or glassy phase states will also be discussed.
Monday, Feb. 24, 2014
Chemical and physical processes controlling organic aerosols and tropopause cirrus: An observational perspective
Dr. Andrew Rollins
NOAA Chemical Sciences Division
Condensed mass in the atmosphere in the form of aerosol and cloud particles is a significant driver of climate and heterogeneous atmospheric chemistry. The processes that control the formation of these particles are complex, and understanding them is frequently limited by the ability to accurately measure the gas and particulate species required to test our theories. In this talk I will discuss results from two recent projects where new analytical instrumentation has been developed and used to inform our understanding of gas/particle partitioning processes involving organic aerosols and cirrus clouds. The first study presented exploits high time resolution measurements of organic nitrate aerosols using a laser induced fluorescence based technique. Laboratory and field measurements using this instrument have been used to probe the influence of nitrogen oxide chemistry on the formation of secondary organic aerosols (SOA) in the troposphere. Observations during the California Nexus (CalNex) field study demonstrate the significance of nitrate radical initiated SOA formation at night, and important nonlinearities in this chemistry.
In the second half of the talk I will discuss measurements of water vapor and ice water content in the tropical tropopause layer (TTL) using a new tunable diode laser based hygrometer operated on the NASA Global Hawk aircraft. Confidence in the accuracy of these historically challenging measurements is strengthened by use of an in-situ calibration system, and excellent agreement with a separate hygrometer operated in parallel. These measurements have provided evidence for the transport of water in excess of saturation through the TTL and into the stratosphere.
Thursday, Feb. 20, 2104
The role of oceanic halogen and sulfur compounds for the middle atmosphere
Dr. Susann Tegtmeier
GEOMAR Helmholtz Centre for Ocean Research Kiel, Kiel, Germany
The decline of anthropogenic chlorine in the stratosphere within the 21st century will increase the relative importance of naturally emitted, very short lived halocarbons on stratospheric ozone destruction. Such halocarbons play a significant role in present day ozone depletion, in particular in combination with enhanced stratospheric sulfate aerosol loading. There is a need to better understand how much of the observed stratospheric halogen and sulfur aerosol originates from natural sources, in particular from oceanic emissions, and how this will change and affect the middle atmosphere in a future climate.
In this talk, I will describe recent advances in our understanding of brominated and iodinated halocarbons based on ship campaign data, modelling studies, and aircraft measurements, including current and future halocarbon emission inventories and their contribution to the stratospheric halogen loading. Similarly, dimethylsulphide emissions are used to assess the impact of naturally emitted sulfur on the stratospheric aerosol loading. One focus of the presentation is on the tropical West Pacific, the main source region for stratospheric air, where highly localized halogen sources and a tropospheric OH minimum were identified. The potential of the latter to amplify the impact of oceanic halocarbons and South East Asian SO2 on the stratospheric composition is discussed. Finally, the ozone-depletion potential weighted emissions of halocarbons will be compared to those of other ozone depleting substances to quantify the overall impact of natural halocarbons on the ozone layer for current day conditions and future scenarios.
Monday, February 17, 2014
Prof. Tim Bertram, UCSD
Chemistry at atmospheric aqueous interfaces: In situ constraints on halogen activation at the air-sea and air-particle interface
Reactions occurring at atmospheric, aqueous interfaces can serve to catalyze reaction pathways that are energetically unfavorable in the gas phase. The reactive uptake of N2O5, a primary nocturnal nitrogen oxide (NOx) reservoir, serves as both an efficient NOx removal mechanism and regionally significant halogen activation process through the production of photo-labile ClNO2. Both the reaction rate and ClNO2 product yield are a complex function of the chemical composition of the reactive surface. To date, analysis of the impact of N2O5 chemistry on oxidant loadings in the marine boundary layer has been limited to reactions occurring on aerosol particles, with little attention paid to reactions occurring at the air-sea interface. Here, we report the first direct measurements of the air-sea flux of N2O5 and ClNO2 made via eddy covariance in the polluted marine boundary layer. The results are combined with in situ determinations of the N2O5 loss rates to aerosol particles and interpreted within a time-dependent coupled atmosphere- ocean model.
Thursday, Feb. 13, 2014
Chemical changes to light absorbing carbonaceous aerosol with oxidative aging
Dr. Eleanor Browne
Light absorbing carbonaceous aerosol (LAC) is one of only two atmospheric components that both degrade air quality and cause climate warming. Due to the short atmospheric lifetime (~days-weeks) of LAC, there has been considerable recent interest in quantifying the climate and health impacts of LAC and developing mitigation strategies that will simultaneously improve climate and human health. Despite this recent interest, large uncertainties in the quantification of LAC’s climate impact remain. In part this is due to the poorly characterized influence of “aging”, the complex atmospheric processes that alter the chemical and physical properties of aerosol over their lifetime.
In this talk, I discuss experiments using vacuum ultraviolet (VUV) ionization-high resolution aerosol mass spectrometry to quantify the kinetics and chemical composition changes to LAC (both black and brown carbon) upon oxidation. In brief, I find that heterogeneous oxidation by OH of the aliphatic compounds present on the surface of black carbon particles occurs quickly (lifetime of ~1 day) and produces oxygenated hydrocarbons. I also present results for the aging of brown carbon generated from the smoldering of pine needles. The primary aerosol emitted from smoldering is highly oxygenated and when it ages in the presence of the gaseous smoldering emissions, a chemically distinct secondary organic aerosol component forms. These results show that LAC undergoes substantial chemical changes on the timescale of a day. Since the chemical changes described here likely have important impacts on the climate-relevant properties of LAC (such as light absorption and hygroscopicity), further quantification of these aging mechanisms and timescales is needed in order to accurately estimate the climate effects of LAC.
Monday, Feb. 10, 2014
Mercury cycling in the atmosphere-ocean-land system: Insights from regional and global modeling
Dr. Yanxu Zhang
Mercury is a neurotoxin that affects public heath primarily through consumption of marine fish and seafood. Anthropogenic mercury emission sources include coal burning and artisanal gold mining. Mercury undergoes long-range transport in the atmosphere and can cycle multiple times in the atmosphere-land-ocean system before eventually buried in the ocean sediment. To attribute the source of mercury in a certain region thus requires an appreciation of the contribution from legacy and external sources. However, our current understanding of the legacy mercury in the land and ocean subjects to large uncertainties. There are also unresolved questions in the atmospheric chemistry of mercury that affect its long-range transport potential. This talk will highlight recent advances in combining regional/global modeling in the atmosphere/ocean and measurements in different environmental compartments to improve understanding of the mercury cycle.
Monday, February 3, 2014
Tech Transfer in the Life Sciences
Brynmor Rees, University of Colorado Technology Transfer Office
Academic research is a creative field in which new ways of thinking often emerge. It is therefore not surprising that many inventions are born out of research. How is it that university inventions can best be transformed into real-world solutions, and what processes have been established to facilitate innovation at CU? Brynmor Rees, a Licensing Manager from CU’s Technology Transfer Office (TTO), will lead a discussion about inventions, intellectual property (including patents), and commercialization at CU. The presentation will include what to do with your invention, information about starting companies, how the patent system works, and real case studies.
Monday, January 13, 2014
Active Learning: Tips for Success.
Jenny Knight, MCD Biology.
Much evidence has been collected over the past 10 years supporting the efficacy of active learning in college science classrooms. However, many instructors who are interested in change still find it challenging to implement successfully. I will present reasons why it's worth trying active learning, and suggest some approaches and techniques that can be easily tried in any class.
Monday, December 2, 2013
Professor, Civil & Environmental Engineering, University of Colorado
Photochemical formation of reactive oxygen species from wastewater organic matter
The study of the physicochemical properties of organic matter has been of interest to researchers in the areas of chemistry and engineering for many decades. Organic matter influences many different processes in the natural and engineered environment, including fate and transport of organic contaminants and the formation of disinfection byproducts. Over the past decade, emphasis has been placed on the study of the physicochemical properties of effluent organic matter (EfOM), which represents the organic matter found in wastewater effluents. The presence of EfOM in wastewater effluents impacts not only the efficacy of engineered processes towards the removal of organic contaminants, but also the natural fate of these compounds in receiving streams. In this presentation, the photochemical formation of reactive oxygen species (ROS) from EfOM will be discussed. The ROS of interest include singlet oxygen (1O2) and hydroxyl radical (HO). The overall quantum yields for the formation of these species as a function of EfOM composition will be discussed, in addition to additional details with regards the photophysical processes responsible for the formation of these species in the complex mixture that is EfOM.
Monday, November 18, 2013
Air Pollution Research Center, University of California, Riverside, CA 92521
Products of OH + furan reactions and some implications for aromatic hydrocarbon atmospheric degradation
Unsaturated 1,4-dicarbonyls are important products of the atmospheric degradations of aromatic hydrocarbons such as benzene, toluene, xylenes and trimethylbenzenes, which comprise ∼20% of the non-methane volatile organic compounds present in urban air masses in the USA. However, in many cases the measured formation yields of the unsaturated 1,4-dicarbonyls are significantly lower than those of the presumed co-product 1,2-dicarbonyls. These discrepancies could be due to analytical problems and/or rapid photolysis of unsaturated 1,4-keto-aldehydes and unsaturated 1,4-dialdehydes, or to incorrect reaction mechanisms for the OH radical-initiated reactions of aromatic hydrocarbons. Since unsaturated 1,4-dicarbonyls are major products of OH + furans, with apparently simpler product distributions and mechanisms, we have investigated the reactions of OH radicals with furan, 2- and 3-methylfuran, and 2,3- and 2,5-dimethylfuran, in the presence of NO. Using direct air sampling atmospheric pressure ionization tandem mass spectrometry and gas chromatography, the unsaturated 1,4-dicarbonyls were observed and quantified. The measured unsaturated 1,4-dicarbonyl formation yields ranged from 8 ± 2% from OH + 2,3-dimethylfuran to 75 ± 5% from OH + furan. Other products were also formed. These data will be presented and discussed and, time permitting, a brief discussion of in situ nitro-aromatic and nitro-PAH formation from the atmospheric degradations of aromatic hydrocarbons and PAHs will also be presented.
Monday, November 11, 2013
Shuichi Ushijima, First Year Graduate Student, Department of Chemistry and Biochemistry, University of Colorado,
A Colorimetric Method to Determine Biological Production of Hydrogen Peroxide
Hydrogen peroxide (H2O2) is the most stable reactive oxygen species (ROS) and is involved in reactions with dissolved organic matter (DOM) and biologically important metals in natural waters. A technique which uses horseradish peroxidase (HRP) and Amplex Red to measure the biological production of H2O2 is tested in this study. In this method, HRP catalyzes the reaction between H2O2 and Amplex Red to produce resorufin, a colored compound, which can be measured using UV-Vis spectrometry. This method is compared to another technique that utilizes the chemiluminescent reaction of H2O2 to acridinium ester. Results from analysis of fresh water samples and cultures of Chlamydomonas reinhardtii will be discussed.
Lucas Algrim, First Year Graduate Student, Department of Chemistry and Biochemistry, University of Colorado
Temperature-Dependent Kinetic And Mechanistic Study Of The Gas-Phase Oxidation Of Select Carbonyls
Carbonyls are common intermediates in the overall oxidation of organic volatile compounds (VOCs), a chemical process that can influence tropospheric ozone production, aerosol formation, and climate change. Understanding carbonyl chemistry is imperative to fully understand and model such processes. To further the current knowledge of carbonyl chemistry, which is lacking for larger branched species, the temperature dependence of the gas-phase reaction of three ketones, 3-pentanone (DEK), 3-methyl 2-butanone (MIPK), and 2,4-dimethyl 3-pentanone (DIPK), with Cl atoms were investigated using an atmospheric smog chamber equipped with FT-IR, PTR-MS, and GC-FID. The ketones’ Arrhenius expressions were found to be: kDEK = 4 ±11 x 10-11 cm3 molecules-1 s-1 e(2 ± 7 kJ/mol)/RT, kMIPK = 7 ±23 x 10-11 cm3 molecules-1 s-1 e(0.2± 8 kJ/mol)/RT, kDIPK = 3 ±110 x 10-10 cm3 molecules-1 s-1 e(-3± 8 kJ/mol)/RT. Within the uncertainties the rate coefficients exhibit no temperature dependence. Product yield analysis of DIPK and MIPK consistently displayed a tertiary α-carbon: primary β-carbon (relative to carbonyl) branching ratio of approximately 70% : 30% for H-atom abstraction by Cl atoms over the investigated temperature range. This indicates a temperature-independent mechanism, consistent with the kinetic measurements.
Monday, November 4, 2013
Amanda McLaughlin, First Year Graduate Student, Department of Chemistry and Biochemistry, University of Colorado
Characterization of copolymers of vinylbenzyl thymine (VBT) and vinylbenzyl chloride (VBC) using size exclusion chromatography
VBT, a versatile monomer, has successfully been copolymerized with vinylbenzyl triethyl ammonium chloride (VBA) to create a material that can be cast as a lasting coating with proven antimicrobial properties on a variety of surfaces. Molecular weight determination of (VBT)n(VBA)m, however, has been presented many difficulties due to the high charge density of VBA. Copolymerization of VBT with VBC will lead to a system that can be fully characterized and subsequently quaternized to yield a polymer with similar utility, but with higher tunability to that of the (VBT)n(VBA)m system. Results of the synthesis of (VBT)n(VBA)m copolymers will be presented.
Size exclusion chromatography (SEC) is a liquid chromatography technique, which allows for the separation and characterization of organic compounds based on size of the molecules. This technique will be utilized for the characterization of copolymers of VBT and VBC, using standard samples of poly-VBC to create a standard curve.
Ingrid Mielke-Malay, First Year Graduate Student, Department of Chemistry and Biochemistry, University of Colorado
Water sensing by localized surface plasmon resonance on HKUST-1 and ZIF-8 multilayer metal organic frameworks
Metal organic frameworks (MOFs) show potential for use in gas sensing and sequestration, with applications in industrial, defense, and biological settings, as well as environmental monitoring. Different gases can be adsorbed into these crystalline networks of organic ligands and metal ions or clusters by changing their sub-nanometer sized pores. An important practical consideration when developing MOFs for gas sensing is the requirement that they operate effectively under humid conditions. Layers of two MOFs, HKUST-1 (Cu3BTC2(H2O)n] and ZIF-8 (2-methylimidazole zinc salt), were formed on silver nanoparticles and the extent to which they adsorbed sample gases and water vapor was determined using localized surface plasmon resonance spectroscopy.
Monday, October 28, 2013
Prof. Jose-Luis Jimenez
Dept. Chemistry & Biochemistry and CIRES, Univ. of Colorado-Boulder
Instrument and Technique Development, Field Studies, and Computer Modeling to Elucidate Organic Aerosol Sources, Properties, Processes, and Fate
In this talk I will present an overview and highlights of research on OA instrumentation, measurements, and modeling by our group since Fall 2008, as well as of upcoming projects of interest to 1st year students. Organic aerosols (OA) account for about 1/2 of the submicron particle mass in the atmosphere leading to important impacts on climate, human health, and other issues, but their sources, sinks, and evolution are poorly understood. OA is comprised of primary OA (POA, emitted in the particle phase) and secondary OA (SOA, formed by gas-to-particle conversion). Together with others in the community and contrary to the understanding at the time, we demonstrated in the mid-2000s that SOA dominates over POA at most locations. This paradigm shift has led to intense research on the sources, processing, properties, and fate of SOA. Because pre-existing and commercial instruments were very limited for the analysis of the complex mixtures of highly oxidized species comprising real SOA, we have developed or co-developed several experimental techniques aimed at extracting more information out of ambient and laboratory air, and pioneered their application in field experiments. These include measurements of eddy covariance fluxes, metals, and fast (millisecond) processes with the Aerodyne Aerosol Mass Spectrometer (AMS), development and application of soft-ionization techniques, measurements of the volatility and gas/particle partitioning of organic species, and measurement of the SOA formation potential of ambient air in real-time. We have also pioneered many data analysis techniques for aerosol mass spectrometry data, including 2 and 3-dimensional factor analysis, techniques for constrained high-resolution ion fitting, and elemental analysis of bulk organics with detection limits 6 orders-of-magnitude better than commercial techniques. We have applied these techniques to characterize POA sources (such as biomass burning, motor vehicles, and cooking) and to analyze ambient air at ground sites and from several aircraft in major field studies such as MILAGRO, SOAR, AMAZE, ARCTAS, DAURE, FLAME-3, CalNex, BEACHON-RoMBAS, DC3, SEAC4RS, and SOAS. We have proposed a new paradigm (Jimenez et al., Science, 2009) that is consistent with worldwide measurements and in which OA and OA precursor gases evolve continuously by becoming increasingly oxidized, less volatile, and more hygroscopic, leading to the formation of oxygenated organic aerosol (OOA), with concentrations comparable to those of sulfate aerosol throughout the Northern Hemisphere. We have used computer box modeling and collaborated closely with several regional and global modelers for deeper analysis and interpretation of field study data. Upcoming projects include development of hyphenated soft-ionization techniques, laboratory research on SOA formation from the NO3 radical and of indoor air chemistry, and a field study in the Amazon.
Monday, October 21, 2013
Demetrios Pagonis, First Year Graduate Student, Department of Chemistry and Biochemistry, University of Colorado
Isoprene Ozonolysis: Secondary Organic Aerosol Formation Pathways and Heterogeneous Aging
Isoprene is the second most abundant volatile organic compound in our atmosphere, behind methane. Isoprene reacts with oxidizing agents in the atmosphere to form secondary organic aerosol (SOA), impacting climate and adversely impacting human health. After formation, SOA particles undergo heterogeneous reactions that age the particles, changing their composition as well as environmentally relevant properties such as size, composition, density, and potential to serve as cloud condensation nuclei. In this research we studied the pathway of isoprene SOA formation as well as the heterogeneous aging of SOA particles using FTIR. The role of the first-generation products methacrolein and methyl vinyl ketone in isoprene SOA formation was studied by comparing SOA formed from these first-generation products to isoprene SOA. Mass spectral data on particle composition were obtained using an Aerodyne Aerosol Chemical Speciation Monitor and illustrated the heterogeneous nature of the reactions that age particles.
Abigail Koss, First Year Graduate Student, Department of Chemistry and Biochemistry, University of Colorado
Measurements of Volatile Organic Compounds by GC-MS in Rural Alabama during the 2013 SOAS Campaign
Volatile organic compounds (VOCs) are a large class of chemicals that are emitted into the atmosphere by both human and natural biological activity. VOCs are comprised of both precursor compounds that drive oxidation chemistry and oxidation products. Extensive measurements of VOCs can help determine the relationships between precursor and secondary compounds, and the relative effects of anthropogenic and biogenic emissions on climate and air quality.
The Southeastern US is a region of particular research interest, as it is strongly affected by both anthropogenic and biogenic VOCs. As part of the 2013 Southern Oxidant and Aerosol intensive study (SOAS), an in-situ gas-chromatograph mass spectrometer (GC-MS) was deployed at a forested site in rural Alabama. This site was dominated by biogenic emissions, but was also subject to anthropogenic influence.
The GC-MS measured a large number of primary and secondary anthropogenic and biogenic VOCs in the C2 to C11 range, with a time resolution of 30 minutes. Measured compounds of particular interest include isoprene, speciated monoterpenes, methylvinylketone (MVK), methacrolein, C2 to C11 alkanes, lightweight unsaturated hydrocarbons including ethene, propene, and acetylene, C6 to C9 aromatics, C1 to C7 oxygenated VOCS (alcohols, ketones, aldehydes), halogenated VOCs, acetonitrile, and several sulfur-containing compounds. A summary of these measurements will be presented. This summary will include characterization of various anthropogenic and biogenic sources sampled at the site, relationships of the most important VOCs to basic meteorological conditions, and diurnal profiles that illustrate shifts in photochemistry and emissions. These GCMS measurements will provide key information for constraints in models and to aid in the interpretation of data from other instruments.
Monday, October 14, 2013
Joost de Gouw, Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder & NOAA Earth System Research Laboratory
Organic Carbon in a Changing Atmosphere: How Our Energy Choices Affect Air Quality and Climate Change
Recording of Seminar (Password-protected; Request password via email from Joost.deGouw@noaa.gov)
Atmospheric emissions associated with the use of energy affect the chemical composition of the atmosphere, and have led to such diverse societal issues as air quality degradation and global climate change. Over the pas decade, resource limitations and concerns over energy security and the environment have led to significant changes in the use of energy in the U.S. The domestic production of oil and natural gas has strongly increased as a result of advances in directional drilling and hydraulic fracturing. Also, ethanol made from corn now constitutes approximately 10% of the volume of gasoline sales in the U.S. In this presentation, we will look at some of the atmospheric implications of these changing energy sources and how they are affecting atmospheric chemistry, air quality and climate change.
Monday, October 7, 2013
Daniel James Cziczo, Victor P. Starr Career Dev. Associate Professor of Atmospheric Chemistry, Massachusetts Institute of Technology
Combining Field and Laboratory Studies to Understand the Dominant Sources and Mechanisms of Cirrus Cloud Formation
The formation of clouds is dependent on the availability of aerosols to initiate the condensation of water vapor. In the case of cirrus clouds, ice nucleation can occur homogeneously at low temperature and high saturation on the vast majority of particles or heterogeneously at high temperature and low saturation on the small fraction of atmospheric aerosols that are efficient ice nuclei (IN). The critical properties that make for a good IN are slowly being established. This work focuses on those particles which have been shown to be important IN through in situ studies: mineral dust and metallic particles are the dominant source of residual particles, whereas sulfate/organic particles are underrepresented and elemental carbon and biological material are essentially absent. We are now undertaking ice nucleation studies using the Droplet Measurement Technologies SPectrometer for Ice Nuclei (SPIN) on mineral dust and metallic aerosol and report ice nucleation conditions. A comparison to the types that are not observed in cirrus and to the onset of homogeneous freezing is made.
Monday, September 30, 2013
Rainer Volkamer, Department of Chemistry and Biochemistry and CIRES Fellow, University of Colorado, Boulder
Marine trace gases and aerosols: novel chemistry at atmospheric interfaces
Discoveries about chemistry in the lower atmosphere are often driven by advances with analytical techniques to measure atmospheric composition. Oceans cover 70% of the Earth surface, yet the remote marine atmosphere remains one of the most poorly probed atmospheric environments on Earth. Ocean emissions of organic carbon molecules (gas- and aerosol phase) and halogens are relevant to climate discussions, because they modify oxidative capacity, i.e., the rate at which climate active gases such as ozone, and methane are removed from the atmosphere. They can further modify aerosols that influence Earth albedo. I will present optical spectroscopic instruments that my group has designed, assembled, and deployed over the past 6 years in laboratory studies of aerosol formation, and field measurements in the tropical atmosphere. These innovative instruments enable measurements of halogen oxide radicals (bromine and iodine oxide), and oxygenated small molecules, and allow us to study their chemical formation pathways, multiphase chemistry, distributions and relevance in the tropical atmosphere. We find that novel chemistry is operative at atmospheric interfaces (ocean surface, and aerosols). Marine organic carbon gases and halogens are particularly relevant in the tropical free troposphere, where most of the tropospheric ozone mass resides, 75% of the global methane destruction occurs, and mercury oxidation rates are accelerated at low temperatures.
Monday, September 23, 2013
Paul Ziemann Professor of Chemistry and Biochemistry & CIRES Fellow, Univ. of Colorado-Boulder
Comprehensive Laboratory Studies of the Chemistry of Secondary Organic Aerosol Formation: Scientific Questions, Techniques and Open Graduate Student Projects
In this talk I will describe for incoming graduate students the atmospheric chemistry research being conducted in my laboratory. Laboratory studies provide much of the fundamental data on reaction kinetics, products, and mechanisms that are needed to achieve a deep understanding of atmospheric chemistry and to develop detailed and accurate models that are used to establish air quality regulations and to predict the effects of human activities on global climate. Research in my laboratory focuses on the atmospheric chemistry of organic compounds emitted from natural and anthropogenic sources and the physical and chemical processes by which oxidized organic reaction products form microscopic aerosol particles. Studies are conducted in large-volume environmental chambers where experiments are designed to simulate but simplify atmospheric chemistry and conditions in order to obtain information on gas and particle chemical composition; gas and heterogeneous/multiphase reaction rates and equilibria; thermodynamic, hygroscopic, and phase properties of particles; and gas-particle-wall interactions. Obtaining such data is a challenge, but in this talk I will describe how we approach this problem by using a diverse array of measurement techniques including real-time and offline mass spectrometry, temperature-programmed thermal desorption, gas and liquid chromatography, NMR, spectrophotometry, and scanning mobility particle sizing. I will then provide examples of our use of these methods to develop quantitative chemical reaction mechanisms of organic gas and aerosol chemistry and models of SOA formation and particle properties such as hygroscopicity, and describe some future research projects for which I am recruiting CU graduate students.
Erin E. McDuffie 1sr Year Graduate Student University of Colorado, Boulder
A New Instrument for the Analysis of Single Aerosol Particles: The Coupling of ATOFMS and LIBS
Knowledge of aerosol particle composition is crucial in order to gain an understanding of health and environmental effects of atmospheric particulate matter, and requires measurements that can provide detailed information about chemical components. An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) is used for the semi-quantitative analysis of the composition of individual atmospheric particles upon laser-induced desorption and ionization. Integration of the spectroscopic technique of Laser-Induced Breakdown Spectroscopy (LIBS), in which light emitted by the elemental components of the particle upon irradiation with a laser is collected, should increase the quantitative data provided by this instrument. Due to the similarities between both techniques, integration of the two should be straightforward and requires only minor additions to the ATOFMS. This presentation will focus on the advantage of coupling these two techniques as well as the inherent physical and electronic challenges, including: plasma generation (excitation laser pulse energy), plasma dynamics in an electric field and vacuum conditions, emission detection (collection angle and distance from the light source), and software program design and implementation. These challenges continue to be systematically addressed in Dr. Deborah Gross’s Lab at Carleton College and are presented here as evidence of the range of issues that arise in producing a new single-particle analysis instrument.
Monday, September 16, 2013
Margaret Tolbert Department of Chemistry and Biochemistry and CIRES
Deliquescence of calcium perchlorate: A route to liquid water on Mars and other possibly habitable planets
The Wet Chemistry Laboratory (WCL) aboard the Phoenix Mars Lander identified the presence of 0.5% perchlorate (ClO4-). Reanalysis of the Viking gas chromatography-mass spectrometry results also suggests perchlorate was present in the soil and the Mars Science Laboratory (MSL) rover has potentially found perchlorate as well. Perchlorate salts are known to readily absorb water vapor from the atmosphere and deliquesce into an aqueous solution. We have previously performed laboratory studies to better understand the deliquescence (crystalline solid to aqueous salt) and also efflorescence (aqueous salt to crystalline solid) of several perchlorate salts at low temperatures. We found that NaClO4 and Mg(ClO4)2 are highly deliquescent, forming aqueous solutions at humidity values as low as 40% RH and at temperatures as low as 223 K. We also observed a significant hysteresis that occurs during efflorescence of these salt solutions, expected due to the kinetic inhibition of crystal nucleation. The efflorescence relative humidity values of sodium and magnesium perchlorate solutions are 13% RH and 19% RH, respectively, indicating that perchlorate salts could exist as stable or metastable aqueous solutions over a wide range of Martian RH and temperature conditions.
Although the low temperature deliquescence of several perchlorate salts is now well characterized, instruments onboard Phoenix and MSL have identified calcium perchlorate (Ca(ClO4)2) as the likely parent salt. Calcium perchlorate is known for its highly deliquescent properties and low eutectic point; however, the deliquescence and efflorescence of this salt have not yet been quantified as a function of temperature. We have used Raman microscopy to examine the deliquescence and efflorescence of Ca(ClO4)2 under relevant Martian temperatures. Results for these experiments will be presented and implications for the availability of liquid water on Mars and similar planets will be discussed.
Robert E. Sievers and team of 35 collaborators sponsored by FNIH and the Bill and Melinda Gates Foundation GCGH
Sievers Group Studies of Needle-free Delivery of Dry Powder Aerosol Vaccines and Pharmaceuticals
Scientists from the University of Colorado and Aktiv-Dry LLC have formulated dry powder vaccines effective against measles. We have developed and patented a system known as CO2-Assisted Nebulization with a Bubble Dryer® (CAN-BD) that stabilizes, micronizes, and dries these and various other biologicals and pharmaceuticals with great success. Based on our success with a variety of biopharmaceuticals, we have demonstrated that Aktiv-Dry’s CAN-BD system can be used to manufacture stable and active dry powders for inhaled vaccines and antibiotics. These dry inhalable powders can be administered through multi-dose or single-dose inhalers (such as Aktiv-Dry’s PuffHaler® or the BD Technologies’ Solovent) and are easy to handle and administer in situations in resource-poor countries. The measles live-attenuated, inhalable dry powder aerosolizable vaccine has been tested in Phase I clinical trials recently successfully completed in Pune, India; the 60 subjects were all dosed by inhaling a single breath of dry powder aerosol beginning in March 2012, and no serious adverse events have been reported to date. No serious adverse events were observed in the studies of the inhaled powder vaccine in macaques or in 60 human volunteers in a Phase I clinical trial.
Wednesday, September 4, 2013
Characterizing the influence of multi-generational chemical processing on organic particles
Christopher D. Cappa, Associate Professor, Dept. of Civil and Environmental Engineering, University of California, Davis
Reactions of organic compounds in the atmosphere with common oxidants (e.g. the hydroxyl radical and ozone) can lead to the formation of secondary organic aerosol (SOA) and can engender transformations within the particle-phase through heterogeneous reactions. The resulting specific chemical composition of the particles can influence their ability to take up water, activate into cloud droplets and absorb and scatter sunlight. Most organic compounds emitted into the atmosphere that are capable of forming SOA are subject to multi-generational oxidation, which simply means that they can react more than once, with each reaction having some probability of functionalizing or fragmenting the parent species. In this seminar, two aspects of this multi-generational ageing will be discussed: SOA models and SOA optical properties. Many models of SOA formation, especially those most commonly used to simulate regional and global SOA burdens do not account for such multi-generational ageing, instead parameterizing SOA formation as a one-step process. And those SOA models that do account for ageing tend to do so in a very ad hoc manner and with little validation (with chemically explicit models being the exception). The Statistical Oxidation Model (SOM) is a reduced complexity SOA model that explicitly accounts for multi-generational ageing in both the gas and particle phases and has been developed to capture the countering effects of fragmentation and functionalization. The basic framework of the SOM will be introduced along with an overview of next-generation developments of the model to make it amenable to use in 3D models. In the second part of this seminar, a series of SOA formation and ageing experiments will be discussed in which particle optical property measurements (light extinction and light absorption) have been made and correlated with particle composition. Our results demonstrate that SOA optical properties are not static and depend explicitly on the identity of the gas-phase precursor.
Monday, May 6, 2013
How can we improve therapy for Tuberculosis?
Mycobacteria Research Laboratories,
Microbiology, Immunology and Pathology Department,
Colorado State University
Tuberculosis [TB] is one of the leading killer infectious diseases today. Eradication of TB depends on the development of shorter and more effective treatment regimens, including novel treatment alternatives combined with classical TB therapies. At present patients with TB are treated daily with high concentrations of multidrug treatment administered by oral route, subcutaneous or intravenous injections. To improve TB control and treatment it is necessary to ease and shorten anti-TB drug regimens. One approach under study is the use of aerosolized drugs and use of drugs the target the host instead of the bacteria also known as host targeted therapy. In our laboratories we use an experimental murine model that allow for aerosolized anti-TB drug efficacy testing. The uses of aerosol delivery of anti-TB drugs which only option at present are to be used as injectables in addition to the use of lung immune modulators as adjuvants for TB chemotherapy will be discussed.
Monday, April 29, 2013
High-Altitude Aircraft Measurements of the Tropical Tropopause Layer from the NASA ATTREX Campaign
Eric Jensen, NASA Ames Research Center
The NASA Airborne Tropical TRopopause EXperiment (ATTREX) is a five-year airborne science program focused on understanding physical processes occurring in the tropical tropopause layer (TTL, ~13-20 km), with an emphasis on understanding the control of the humidity of air entering the stratosphere. The long-duration Global Hawk Unmanned Aircraft System is used to make measurements of water vapor, clouds, meteorological conditions, numerous chemical tracers, radiative fluxes, and BrO. During February-March, 2013, six 24+ hour flights were conducted from Dryden Flight Research Center to the tropical eastern and central Pacific. Our primary mode of operation was to repeatedly ascend and descend through the TTL (between about 45 and 60 kft). Over 100 vertical profiles were obtained during the six flights, providing a unique, high spatial-resolution dataset of TTL composition. Some of the flights provided surveys of TTL composition, extending well into the southern hemisphere. Other flights targeted thin cirrus near the tropopause forming in anomalously cold regions. Examples of ATTREX measurements will be presented with an focus on TTL relative humidity and clouds. Plans for deploying the Global Hawk to Guam for western Pacific measurements in 2014 will also be discussed.
Monday, April 22, 2013
An Overview of the OASIS 2009 Campaign, with Focus on Halogen, OVOC and Relative Nitrogen Chemistry
John Orlando and Frank Flocke, UCAR, Boulder, Colorado
This talk will present results from the Ocean-Atmosphere-Sea Ice-Snowpack (OASIS) intensive, conducted in Barrow, AK in the spring of 2009. A brief overview of the campaign and the unprecedentedly detailed data set collected in Barrow will be presented.
We have developed a detailed chemical mechanism to simulate the photochemistry during the campaign, which is often dominated by halogen chemistry. In addition, surface production and fluxes of VOC are assessed and compared with ambient measurements both in the gas phase and the snow phase.
In light of these findings, we will discuss “the PAN conundrum,” a long-known discrepancy between predicted and observed PAN mixing ratios in the Arctic coastal boundary layer. We have been working to solve this problem using our detailed zero-D chemistry model. Preliminary results will be shown and discussed.
Monday, April 15, 2013
Real-time organic aerosol formation and oxidative aging using a flow reactor in a ponderosa pine forest
Brett Palm, University of Colorado, Boulder, Department of Chemistry and Biochemistry
A Potential Aerosol Mass (PAM) flow reactor is used in combination with an Aerodyne High Resolution Time-of-Flight Aerosol Mass Spectrometer (AMS) to characterize biogenic secondary organic aerosol (SOA) formation and aging in a terpene-dominated forest during the July-August 2011 Bio-hydro-atmosphere interactions of Energy, Aerosols, Carbon, H2O, Organics & Nitrogen - Rocky Mountain Biogenic Aerosol Study (BEACHON-RoMBAS) field campaign at the U.S. Forest Service Manitou Forest Observatory, Colorado. Ambient air is sampled through the PAM reactor, inside which a chosen oxidant (OH, O3, or NO3) is generated and controlled over a range of values up to 10,000 times ambient levels. High oxidant concentrations accelerate the oxidative aging of volatile organic compounds (VOCs), inorganic gases, and existing aerosol, which leads to repartitioning with the aerosol phase. PAM oxidative processing represents from 1 to more than 20 days of equivalent atmospheric aging during the ~3 minute reactor residence time. During BEACHON-RoMBAS, PAM photooxidation enhanced SOA at intermediate OH exposure (1-10 equivalent days) but resulted in net loss of OA at long OH exposure (10+ equivalent days), demonstrating the competing effects of functionalization vs. fragmentation (and possibly photolysis) as aging increases. Similarities in common SOA oxidation tracers (f44 vs. f43 and Van Krevelen diagram [H/C vs. O/C] slopes) between ambient and PAM-processed aerosols suggests the PAM reactor employs oxidation pathways similar to ambient air. A simple model calculating expected SOA formation from complete consumption of the most abundant VOCs measured at the forest site (monoterpenes, sesquiterpenes, and toluene) consistently underpredicts the amount of SOA formed in the PAM reactor in the field observations. This suggests one or more issues, such as additional SOA sources or formation pathways.
Monday, April 8, 2013
Investigating and improving the freeze-thaw stability of vaccines with aluminum-containing adjuvants: Case studies with model HBsAg vaccines
Prof. LaToya Jones-Braun, School of Pharmacy, University of Colorado Health Sciences Center
Vaccines with aluminum-containing adjuvants, the most prevalent class of adjuvant in childhood vaccines, are susceptible to reduced efficacy if frozen. Accidental freezing of such vaccines have been documented globally, including in the US. This seminar will focus on research related to the freeze-thaw stability of model hepatitis B vaccines. Efforts to both understand the causes of the freeze-thaw instability as well as approaches to improving the robustness of the vaccine following exposure to subzero temperatures will be discussed.
Thursday, April 1, 2013
Special Analytical & Environmental Chemistry Seminar CIRES Auditorium, noon, Thu 3-April *** note unusual day and location ***
Nicole Riemer, Univ. of Illinois @ Urbana-Champaign
Understanding black carbon climate impacts using a stochastic particle-resolved model
Abstract: Black carbon (BC) aerosol influences climate in a number of complex ways. This includes the direct absorption and scattering of sunlight as well as impacts on the cloud microphysical properties. A key factor in quantifying the BC-climate impact is understanding the mixing state evolution of BC aerosol. The mixing state describes whether BC exists as pure particles or in combination with other species within one particle. Experimental evidence shows that BC can exist in very complicated mixtures, and that the precise mixture composition dramatically alters the effects and lifetimes of BC in the atmosphere. For example, sulfate coatings can enhance the CCN activation properties of BC, which facilitates the removal of BC through rainout, lessening the BC impact. On the other hand, coatings can focus radiation on BC nuclei, increasing the absorption effects of BC, thereby enhancing the BC impact. Tracking the mixing state in conventional aerosol models requires treating a multidimensional size distribution, which is computationally prohibitive. Therefore current models usually assume an internal mixture within one mode or size section. The uncertainties associated with this assumption, which artificially coats freshly emitted particles instantly, are not well quantified. This results in current aerosol models using or predicting widely varying rates of “aging” of BC particles from fresh emissions to coated aged particles.
In this seminar I will present an aerosol model of a new type, the stochastic particle-resolved model PartMC-MOSAIC. This model tracks individual particles as they undergo chemical and physical transformations in the atmosphere. Hence aerosol impacts that depend on per-particle composition can be represented in detail. I will illustrate the usefulness of this new approach by focusing on the aging process of black carbon. Using PartMC-MOSAIC we are able to quantify the individual processes that contribute to the aging of black carbon and demonstrate the effect of aerosol mixing state on aging time scales, optical properties, and CCN activation properties.
Monday, March 18, 2013
Ivan Ortega, University of Colorado, Boulder, Department of Chemistry and Biochemistry
Maximizing the information of ground based remote sensing measurements: trace gases and aerosol properties
Over the past few years the Atmospheric Trace Molecule Spectroscopy Laboratory (ATMOSpeclab) at CU Boulder has designed and deployed portable, high-sensitivity Multi Axis Differential Optical Absorption Spectroscopy (MAX-DOAS) instruments with a two-fold purpose: 1) to retrieve profile information of trace gases (i.e., NO2, HCHO, HONO, CHOCHO) and 2) to determine multi wavelength aerosol properties. Past MAX-DOAS measurements have extensively focused on the unique ability to derive information about trace gases; however, this technique can be expanded towards the retrieval of aerosol optical and microphysical properties. This talk presents the evaluation of a novel 2 dimensional MAX-DOAS instrument. The new instrument measures solar scattered light in the horizontal (varying azimuth angle), as well as the vertical plane (varying the elevation angle) which can be used to obtain effective aerosol microphysical properties, such as aerosol size distribution, phase function and refractive index; in addition to the trace gas and aerosol extinction profiles. The 2D MAX-DOAS was deployed and operated for 6 weeks at Cape Cod, MA as part of the Two Column Aerosol Project (TCAP). The TCAP deployment provides unique opportunities for comparisons with aerosol extinction profile measurements by the NASA Langley airborne High Spectral Resolution Lidar (HSRL), Aerosol Optical Depth by a co-located NOAA Multifilter Rotating Shadowband Radiometer (MFRSR) instrument, as well as in-situ measured optical properties aboard DoE’s G1 aircraft. A retrieval was developed to invert effective radius and complex refractive index of particles for monomodal logarithmic normal distribution derived from Mie-scattering calculations in the size range of 0.1-1um. Aerosol extinction retrieved from MAX-DOAS measurements can be compared with extinction predicted by Mie theory to test the assumption of particle homogeneity and sphericity.
Monday, March 4, 2013
Megan L. Melamed, IGAC Executive Officer, University of Colorado, CIRES, Boulder, CO
Overview of the International Global Atmospheric Chemistry (IGAC) Project
The International Global Atmospheric Chemistry (IGAC) Project was formed in 1990 to address growing international concern over rapid changes observed in Earth's atmosphere. IGAC operates under the umbrella of the International Geosphere Biosphere Programme (IGBP) and is jointly sponsored by the international Commission on Atmospheric Chemistry and Global Pollution (iCACGP). IGAC coordinates and fosters atmospheric chemistry research towards a sustainable world by facilitating international collaboration of atmospheric chemistry and multi-disciplinary research, coordinating the synthesis, assessment, and summary of research, cultivating the next generation of atmospheric chemist, and acting as the liaison between the atmospheric chemistry community and the broader Earth System Sustainability community. In July 2012, the IGAC International Project Office relocated to the Cooperative Institute for Research in Environmental Studies (CIRES) at the University of Colorado. Current IGAC activities and how to get involved in IGAC will be presented.
The Impact of Megacities on Air Pollution and Climate Change
As of 2008, for the first time, the majority of the world’s population is living in urban areas , many in megacities (with populations over 10 million). Currently, urban population fractions are higher in developed than developing countries. However, with most of the world population growth expected to occur in developing countries, urbanization is increasing at a higher rate in developing countries. These dramatic increases in population and urbanization, especially in the developing world, have been accompanied by technological and economic growth and development, yielding changes in land use, energy use, and transportation. The resulting changes due to urbanization have dramatic impacts on anthropogenic and biogenic emissions and have notably altered local to global-scale atmospheric composition, increasing the importance of understanding the impacts of urbanization on atmospheric chemistry. In light of the importance of megacities on atmospheric chemistry, the International Global Atmospheric Chemistry (IGAC) Project and the World Meteorological Organization (WMO) released in January 2013 the first comprehensive assessment of Atmospheric Chemistry in Megacities. An overview of this assessment will be presented.
Monday, February 25, 2013
Prof. Waleed Abdalati, Geography Department and CIRES, University of Colorado Boulder
From the Terrestrial to the Celestial: My Perspectives and Experiences as NASA Chief Scientist
For decades, NASA has been an iconic inspiration to the nation and the world, exploring our planet, the space environment, the solar system, and the universe. Success in these endeavors has been built on a foundation of science, technology and engineering that is producing such remarkable achievements as: landing a one-ton rover on the surface of Mars, developing a telescope that will peer 13.5 billion years into the past, and most importantly, providing comprehensive insights into the behavior and evolution of planet Earth. Enabling these capabilities, and the associated research, requires much more than technical and scientific advances, however. It involves a complex balancing of priorities and resources, as well as alignment among a diverse group of passionate stakeholders – all against a backdrop of political and policy turmoil. As chief scientist, it was my responsibility to help shape NASA’s direction, and work to achieve alignment among the interests and objectives of the scientific community, the White House, Congress and others. In this talk, I will discuss some of these challenges and the associated rewards as well as the role science plays at NASA, and the role NASA science plays in the broader national framework.
Monday, February 18, 2013
Prof. Brian Majestic University of Denver
Using iron isotopes as a tool to identify sources of atmospheric iron: an analysis of desert, urban, and oceanic environments
Atmospheric transport followed by deposition of aerosol Fe is the primary source of Fe for much of the surface ocean. In many parts of the ocean, Fe serves as a limiting nutrient for phytoplankton growth, as well as other aquatic organisms. Most aerosol Fe, by mass, is crustally-derived, the majority of which is generated in the Sahara and other deserts. However, solubility measurements show that this crustal-derived Fe is highly insoluble (< 1%), possibly limiting its bioavailability. Two other sources of Fe, biomass burning and combustion-derived anthropogenic aerosols, are characterized by a much higher solubility, so in spite of their lower mass of Fe, they may represent an important contribution to overall bioavailable Fe in the surface oceans.
A new tool to determine the relative importance of these sources is Fe isotope analysis. Previous work has shown that crustal material has an isotopic composition equal to ~ 0.1 ‰. Therefore, isotopic deviations from 0.1 ‰ may indicate the presence of non-crustal Fe. In this talk, I will present Fe isotope data from the outskirts of Phoenix, AZ, a highly crustal environment as well as Bermuda, a pristine oceanic site. Bermuda is an ideal site to test this method because, during the summer months, the air masses reaching Bermuda originate from West Africa (crustal) and, during the winter months, the air masses originate from North America (more anthropogenic). Striking similarities between these two sites, as well as other Fe isotope studies, will be highlighted.
Monday, February 11, 2013
Professor Neil M. Donahue
Departments of Chemistry, Chemical Engineering and Engineering and Public Policy Director, Center for Atmospheric Particle Studies Carnegie Mellon University
Old Aerosols Never Die, They Just Get Oxidized
Organic aerosols comprise a highly dynamic system of multiphase oxidation chemistry. A major element in the organic-aerosol lifecycle is the progressive oxidation of semi-volatile vapors. Oxidation influences the total aerosol mass by forming products with different vapor pressures than their precursor molecules, but the overall effect on the aerosol mass is nuanced. Oxidation (aging) can clearly enhance aerosol mass via formation of more heavily functionalized products, but it can also reduce the aerosol mass as carbon backbones are fragmented, especially later in the oxidation sequence. We have investigated a number of model systems as well as representative bulk aerosol systems to investigate this process, and developed a reduced chemical mechanism to describe it. In addition to influencing the overall mass, oxidation chemistry can produce small amounts of extremely highly oxidized organic vapors. These highly functionalized molecules can and do participate in the formation of molecular clusters (typically involving sulfuric acid in the atmosphere) and their subsequent growth to ultrafine particles and then to particles large enough to have significant health and climate effects. We have recently joined the CLOUD consortium at CERN to study this particle physics.
Monday, February 4, 2013
Dick and Jean Bedell, Boulder, Colorado
India From an Elephant's Back
This presentation reflects observations of a fascinating country and culture by a Boulder couple. Dick and Jean Bedell have volunteered their medical services for several months each year over three decades. Through Rotary Clubs in India and United States, they helped establish a home for girls whose prostitute mothers died of AIDS, and a Hospice Centre staffed by 300 volunteers. They provide seminars for doctors, midwives and nurses in urban and rural facilities. Through Dr. Robert Sievers, they toured the amazing facility in Pune linked with his research on measles vaccine. Their presentation is informal with time for questions.
Monday, January 28, 2013
Roy (Lee) Mauldin, ATOC/INSTAAR, University of Colorado, Boulder
The X Files: Oxidation via Criegee radicals – From reactions to global impacts
Oxidation processes in Earth’s atmosphere are tightly connected to many environmental and human health issues and are essential drivers for biogeochemistry. Oxidation processes remove natural and anthropogenic trace gases and air pollutants from the atmosphere, and produce low-volatility vapours that control secondary aerosol formation and atmospheric production of cloud condensation nuclei. These atmospheric oxidation processes are typically thought to be dominated by three main oxidants: ozone, hydroxyl radical (OH) and nitrate radical. Field measurements however have shown discrepancies between measurements and models indicating the presence of other mechanisms. Our group has recently shown that products formed from the ozonolysis of biogenic alkenes (most likely stabilized Criegee radicals) have a substantial oxidizing capacity, with the ability to oxidized compounds such as SO2 or dimethyl sulphide. This new “X-chemistry” can have significant, or even dominant, contribution to formation of low-volatility inorganic (sulfuric acid) and, most strikingly, very highly oxidized condensable organic vapours. This new route to the formation of sulfuric acid and extremely low-volatility organic compounds can have a considerable impact to global budgets of cloud condensation nuclei. Our observations point toward a highly important, yet unexplored area of atmospheric chemistry and indicate the discovery of a new natural negative feedback mechanism that could partially counteract climate warming.
Monday, December 10, 2012
Laboratory Astrochemistry: Kinetics Studies and Instrument Modifications
Reactions involving organic molecules are important to astrochemistry and astrobiology alike. Several carbon- and nitrogen-containing anions (CN–, C3N–, and C5N–) as well as trans methyl formate have been spectroscopically detected in the interstellar medium (ISM), and this work focuses on relevant gas phase reactions involving these species. The tandem flowing afterglow-selected ion flow tube (FA-SIFT) was used to experimentally determine the rate constants and products of these reactions, and theoretical calculations were conducted to further understand their mechanisms. Additionally, an ion trap mass spectrometer has been modified to allow for the study of ion-neutral reactions. The building of this modification as well as future plans for this instrument with respect to astrochemistry will be discussed.
Monday, November 26, 2012
SOA formation from volatile OVOC
Glyoxal has potentially large sources from remote to polluted environments. Glyoxal is highly water-soluble; it may undergo a series of aqueous-phase processes in aerosol liquid water and lead to the formation of highly oxidized, high-molecular-weight compounds. In the present work, the multi-phase behavior of glyoxal is probed from chamber experiments (PSI chamber, Switzerland) to ambient environments (sub-urban Hong Kong). Phase transfer and subsequent aqueous-phase processes are simulated using a box-model. In both cases glyoxal is found to form secondary organic material under humid condition, which may be affected by various factors such as aerosol acidity and sulfate. This modeling work provides reasonable interpretations for observations and insights into the complicated processes of such a simple molecule.
Monday, November 12, 2012
Theodore Konstantinos Koenig
Separation of Water Spin Isomers by Adsorption
I will be presenting on work to determine whether water spin isomers can be enriched in the gas phase by selective adsorption. I will begin by briefly outlining the motivations and previous literature on the topic. I will then give information on the construction and testing of an instrument for the purpose of examining any effect by a variety of spectroscopies. Finally, initial FT-IR results will be presented to give a preliminary answer to whether selective adsorption does in fact occur.
Monday, October 29, 2012
Effective Henry’s Law Constant Measurements for Glyoxal in Model Aerosols Containing Sulfate
I am going to present results of an atmospheric simulation chamber study on the reversible partitioning of glyoxal, which was studied by direct measurements of gas-phase and particle-phase concentrations for the first time in model aerosols containing sulfate. Two complimentary methods for the measurement of glyoxal particle-phase concentrations are compared: 1) An offline method utilizing filter sampling of chamber aerosols followed by HPLC-MS/MS analysis and 2) Positive Matrix Factorization (PMF) analysis of AMS data. Ammonium sulfate and internally mixed ammonium sulfate/fulvic acid seed aerosols were used to study the influence of seed chemical composition on effective Henry’s law constants (KH,eff) of glyoxal under varying Relative Humidity (RH) and radiation conditions. KH,eff was found to increase exponentially with ammonium sulfate concentration or sulfate ionic strength, I(SO42-), respectively. A Setschenow type plot revealed that glyoxal is subject to a “salting-in” effect in aerosols. Further, the temporal behavior of the reversible uptake of glyoxal on seed aerosols can be described by two distinct reservoirs for monomers and higher molecular weight species filling up at two different characteristic time constants.
3D model simulations of glyoxal-SOA formation over California
Most studies investigating the formation of SOA from glyoxal so far employed simple box model and pseudo-lagrangian approaches, which lack a comprehensive description of emissions variability and transport phenomena. We investigate regional scale variability of glyoxal SOA using the online-coupled regional chemistry transport model WRF/Chem with a focus on the summer 2010 over California. In my talk I will highlight improvements made to the model to better represent glyoxal formation pathways, discuss model performance when compared against a variety of measurement data available from the CalNex and CARES field campaigns, and show how we extend it by two different methods to describe formation of SOA from glyoxal. Finally I will present first results of simulations made for a selected period in June 2010.
Monday, October 22, 2012
University of Colorado at Denver
Investigating O3-initiated heterogeneous oxidation of linoleic acid using ATR-IR flow reactor
Despite recent extensive studies towards heterogeneous oxidation of unsaturated organics (mostly oleic acid) initiated by ozone, little is known about effects of environmental conditions such as ambient temperature and relative humidity; physical state; and oxidant concentration on heterogeneous reaction kinetics. In this work, we used linoleic acid as a proxy for atmospheric unsaturated organics to investigate its heterogeneous oxidation by O3 over a wide range of temperatures (258-314 K), relative humidities (0-80% RH) and ozone concentration (50 ppb -50ppm). Our experiments were carried out using a flow reactor coupled to an attenuated total reflection infrared spectrometer (ATR-IR). Pseudo-first order rate constants and overall reactive uptake coefficients were acquired from absorbance changes in peaks located near 1743 cm-1; 1710 cm-1; 1172 cm-1 and 1110 cm-1, which can be assigned to C=O in ester; C=O in acid; C-C and C-O stretching modes, respectively. Results showed that the kapp and γ increased with increasing temperatures. It was noted the temperature enhancement effect on the reaction kinetics was much more pronounced at lower temperatures. Such behavior can be explained by change in physical state of LA at lower temperatures. In addition, kapp and γ were enhanced by 2-fold as RH increased from 0 to 80%. Moreover, the effect of ozone concentration on the reaction kinetics was reported for the first time. kapp was found to display a Langmuir-Hinshelwood dependence on ozone concentration. Furthermore, yields and hygroscopic properties of reaction products were also investigated by FTIR spectroscopy. The intensity ratio of two C=O stretching bands, A1743/A1710, which was utilized as an indicator of the product yields, increased sharply with increasing temperatures in the lower temperature region (258-284 K), and then remained nearly constant in the higher temperature region (284-314 K). The product yields showed no significant variation with RH, for the intensity ratio of A1743/A1710 barely changed in the wide RH range of 0-80%. Water uptake studies showed that the LA thin film absorbed water with an increasing RH, and the hygroscopicity of the thin film was enhanced after ozone exposure.
Monday, October 15, 2012
Formation of Gold Nanoparticles and Nanorods Analyzed by SEIRA
The goal of this research was to develop the best gold nanostructures for applications in a range of biological, medical, catalytic, environmental, and nanotechnological applications, these were then analyzed using surface-enhanced infrared absorption spectroscopy (SEIRA). Various nanostructures were formed by evaporating gold in vacuum onto CaF2 substrates at deposition angles ranging from incident to 85. Nanostructures were characterized with AFM, SEM, and UV/Vis-NIR spectroscopy. A monolayer of p-nitrobenzoic acid was deposited onto the gold nanostructures to determine the degree of vibrational enhancement in SEIRA. SEIRA enhancement factors of x20-50 were obtained from metal nanostructures formed by the evaporation of 5-7 nm of gold at incident angle. Gold nanorods aggregated during formation at grazing angles and did not yield larger enhancement factors. Further studies on the gold nanorods are being performed to form nanorods with better enhancement factors, which include different techniques in vapor deposition.
Tailoring Porous Silicon for Analyte Response
To better assess and characterize the sensing properties of porous silicon (pSi), we have developed a strategy to create small spatially heterogeneous areas on a pSi surface that exhibit different degrees of surface oxidation by pin printing 9:1 H2O2:glycerol on the prepared pSi surface. The pSi surface chemistry and the heterogeneity of these pin printed regions were assessed using FT-IR microscopy and epi-luminescence microscopy, coupled with multispectral imaging. The results show that the pin printed areas are chemically heterogeneous across their ca. 300 μm diameter and the photoluminescence response to analyte depends on the analyte type and on the spatial position within the printed region (i.e., on the exact extent of oxide formation (Si-O-Si, O2SiH, O3SiH and Si-OH vs. SiH, SiH2 and SiH3) at the pSi surface). The combination of pin printing and multispectral microscopies allows us to create the entire range of pSi chemical compositions and simultaneously assess their performance all within a single 300 μm diameter printed feature. This can lead to more sophisticated pattern recognition schema to allow simultaneous analyte identification and quantification.
Monday, October 8, 2012
Investigating the Chemical Complexity of the Interstellar Medium
I have collected and analyzed to rotational spectrum of methyl ethyl ketone (MEK) from 8 GHz to 1THz. This molecule contains similar functional groups to other known interstellar molecules such as acetone, acetaldehyde, and ethanol, and is therefore a likely product of interstellar organic chemistry. The microwave spectrum for MEK was acquired using the chirped-pulse waveguide Fourier Transform Microwave (FTMW) spectrometer at New College Florida, and the millimeter and submillimeter spectrum was acquired using the direct absorption flow cell spectrometer at Emory University. I will report on the preliminary results of the laboratory spectral analysis.
Development of Novel Sampling Systems for Direct Analysis in Real Time Ionization Sources
Direct Analysis in Real Time (DART) is an ambient ionization source for mass spectrometry (MS) that is utilized in a wide variety of applications including food science, forensics, homeland security, and environmental analysis. Introduced in 2005, DART-MS does not require sample preparation and allows the analysis of solid and liquid samples in their native state. This talk will discuss the development of novel methods of sampling with the DART source to enhance its capabilities. Such methods include rapid heating of samples of metal substrates, ambient ion transfer tubes for non-proximate sensing, and magnetic automated sampling systems for the analysis of powders.
Monday, October 1, 2012
Professor of Chemistry and Biochemistry, Univ. of Colorado-Boulder (starting June 2013)
Professor, Univ. of California Riverside (present)
Comprehensive Laboratory Studies of the Chemistry of Secondary Organic Aerosol Formation: Scientific Questions, Techniques and Open Graduate Student Projects
In this talk I will describe for incoming graduate students the atmospheric chemistry research being conducted in my laboratory. Laboratory studies provide much of the fundamental data on reaction kinetics, products, and mechanisms that are needed to achieve a deep understanding of atmospheric chemistry and to develop detailed and accurate models that are used to establish air quality regulations and to predict the effects of human activities on global climate. Research in my laboratory focuses on the atmospheric chemistry of organic compounds emitted from natural and anthropogenic sources and the physical and chemical processes by which oxidized organic reaction products form microscopic aerosol particles. Studies are conducted in large-volume environmental chambers where experiments are designed to simulate but simplify atmospheric chemistry and conditions in order to obtain information on gas and particle chemical composition; gas and heterogeneous/multiphase reaction rates and equilibria; thermodynamic, hygroscopic, and phase properties of particles; and gas-particle-wall interactions. Obtaining such data is a challenge, but in this talk I will describe how we approach this problem by using a diverse array of measurement techniques including real- time and offline mass spectrometry, temperature-programmed thermal desorption, gas and liquid chromatography, NMR, spectrophotometry, traditional elemental analysis, pycnometry, and scanning mobility particle sizing. I will then provide examples of our use of these methods to develop quantitative chemical reaction mechanisms of organic gas and aerosol chemistry and models of SOA formation and particle properties such as hygroscopicity, and describe some future research projects for which I am recruiting CU graduate students to start in my group in June 2013.
Monday, September 24, 2012
Robert E. Sievers and team of 30 collaborators sponsored by FNIH and the Bill and Melinda Gates Foundation GCGH
CU’s Inhalable Dry Powder Aerosol Measles Vaccine Now In Clinical Trials
Several hundred children die every day from measles-related disease throughout the world and particularly in poor contries. We have developed a Measles Vaccine, Dry Powder (MVDP) and PuffHaler® a novel dry powder inhaler for respiratory delivery to overcome the safety and vaccine wastage problems associated with the current injectable vaccine. Phase I clinical trials of our new inhalable dry aerosol measles vaccine are now underway in 60 adult volunteers. So far there has not been observed or reported any serious adverse events, but the observation interval is not yet ended. MVDP was manufactured from bulk liquid, live attenuated, measles vaccine using CAN-BD® to yield a stable, dry powder, with fine particles suitable for aerosolization and delivery to the pulmonary tract by inhalation. This was achieved by substituting myo-inositol for sorbitol as a stabilizing sugar that is less hygroscopic. Contact with water is detrimental to the stability of measles vaccine and the microparticles are reconstituted only when they deposit in the moist surfaces of the respiratory tract. There is no need for purified water to be carried to remote locations. The stabilization and CAN-BD drying of other vaccines are now being explored. The measles vaccine shelf life is excellent at 2 to 8 °C with only about 0.5 log loss of activity after more than 2 years. At 25 °C, there is approximately only 0.8 log loss after 6 months of storage.
Reactive trace gases in tropospheric chemistry and climate – recent results and upcoming projects
Reactive trace gases and aerosols are relevant components of tropospheric chemistry and climate. Bromine and iodine oxide radicals, and oxygenated VOC species modify HOx radical abundances, influence the reactive chemistry and lifetime of climate active gases (e.g., ozone, methane, dimethyl sulfide) and can trigger the atmospheric deposition of mercury to ecosystems. Reactive trace gases are also a source for secondary aerosol mass that modifies aerosol optical properties, and cloud interactions (Earth albedo). In this talk I will summarize research in the development of innovative optical spectroscopic instrumentation (in-situ and remote sensing) to measure trace gases and aerosols, their applications in field and laboratory measurements conducted by our group in 2012. These include ongoing data analysis and modeling of the TORERO, TCAP, WACS field projects, mechanistic studies in simulation chambers of secondary organic aerosol (SOA) formation, and heterogeneous chemistry of OVOC volatilization from surfaces coated with organics in flow tubes. Future opportunities exist as part of these ongoing data analysis and modeling activities, with simulation chamber experiments at facilities in Boulder and Switzerland (PSI 2013), and to further develop the University of Colorado Airborne Multi AXis Differential Optical Absorption Spectroscopy instrument (CU AMAX-DOAS) in preparation for field projects aboard research aircraft over the western tropical pacific ocean (CONTRAST 2014).
Monday, September 17, 2012
The Importance of Dissolved Organic Matter to the Binding of Copper and the Release of Trace Elements from Coal Ash
The bioavailability and toxicity of copper to aquatic life depends on its speciation. Dissolved organic matter (DOM) plays an important role in the speciation of copper, but there is still much uncertainty about what controls the strength and formation of the Cu2+-DOM complex. The ratio of copper to DOM is known to affect the strength of Cu2+-DOM binding, but previous methods to determine Cu2+-DOM binding strength have generally not measured binding constants over the same Cu:DOM ratios, making these results difficult to directly compare. A competitive ligand exchange-solid phase extraction (CLE-SPE) method and a copper ion-selective-electrode (Cu-ISE) method were used to determine conditional stability constants for Cu2+-DOM binding at near neutral pH and 0.01 M ionic strength over a range of Cu:DOM ratios that bridge the detection windows of previous measurements reported in the literature. As the Cu:DOM ratio increased from 0.0005 to 0.1 mg Cu (mg DOM-1), the measured conditional binding constant (cKCuDOM) decreased from 1011.5 to 105.6 M-1. This behavior is consistent with the presence of Cu2+ binding sites of higher affinity and lower abundance that become filled as the total copper concentration increases. A comparison of the binding constants measured using CLE-SPE with those measured by Cu-ISE and voltammetry methods demonstrates that the Cu:DOM ratio is an important factor controlling the Cu2+-DOM binding strength for a variety of DOM isolates and whole water samples.
Using correct Cu2+-DOM binding constants to accurately model copper speciation is important for predicting copper toxicity in cases like the waters draining the Pebble deposit in southwestern Alaska, where small increases in the dissolved copper concentration may be harmful to salmonids and other aquatic biota. Experimentally determined Cu2+-DOM binding constants were used as inputs in Visual MINTEQ to model copper speciation and calculate Cu2+ concentrations. The results were then compared to results from the biotic ligand model (BLM), a speciation and toxicity model recommended by U.S. EPA for calculation of stream copper standards, which uses the Windermere Humic Aqueous Model (WHAM) to model metal interactions with DOM. The BLM was found to over-estimate Cu2+ at low total copper concentrations and under-estimate Cu2+ at high total copper concentrations, which may result in over- or under-estimations of toxicity.
DOM also has also been shown to enhance the dissolution of soils, sediments and minerals, which could result in the release of toxic trace elements into aqueous systems. Coal ash contains high concentrations of toxic trace elements that may have the potential to be released into the water. Releases of coal ash to rivers and streams, such as that which occurred from the Kingston Fossil Plant in Kingston, TN, into the Emory and Clinch Rivers in December 2008, are a concern because of the potential for human health problems, as well as ecological effects. In order to understand the effect that DOM has on the release of trace elements from coal ash, a series of release experiments were performed using coal ash generated from the Kingston Fossil Plant as a function of DOM concentration, DOM aromaticity, and calcium concentration. Various DOM isolates and filtered site-water samples collected near the Kingston Fossil Plant were used to produce coal ash suspensions at a fixed ash:water ratio of 1:1000 and a near-neutral pH. The major and trace elemental composition of the solution, and specific trace metals (mercury, lead, copper, aluminum) and metalloids (arsenic and selenium) were measured. The results indicate that DOM enhances the release of mercury, lead, copper, and aluminum from coal ash. The concentration of mercury, copper and aluminum released from the coal ash was positively correlated with the SUVA254 (ultraviolet absorbance at 254 nm divided by the dissolved organic carbon concentration) of the DOM. The release of arsenic and selenium from the coal ash was not dependent on the DOM concentration or SUVA254. Calcium was shown to inhibit the release of mercury, copper and aluminum from the coal ash
Monday, September 10, 2012
Jose L. Jimenez
Organic aerosol sources and processing in the atmosphere: recent results and upcoming projects
Organic aerosols (OA) account for about 1/2 of the submicron particle mass in the atmosphere, but their sources, sinks, and evolution are poorly understood. OA is comprised of primary OA (emitted in the particle phase) and secondary OA (formed from chemical reactions of gas-phase species). In this talk I will summarize research in OA instrumentation, measurements, and modeling by our group over the last year. This includes ongoing analysis and modeling of the recent CalNex-LA, BEACHON-RoMBAS, and DC3 field projects, direct measurements of the SOA formation and photochemical evolution of ambient air using the Potential Aerosol Mass (PAM) flowtube, model/measurement comparisons to constrain the OA budget, and results from our new MOVI-CIMS instrument which allows molecular-level analysis of OA with high sensitivity and mass resolution. Finally, I will introduce future projects in our group, including an update on the design of the new shared smog chamber facility in the Cristol building (to be completed in May 2013), upcoming field projects in the Alabama (SOAS 2013) and the Amazon (GoAmazon 2014), and a new ion mobility spectrometer – CIMS instrument coupling.
The Ins and Outs of Ice Nucleation
Depositional ice nucleation on atmospheric aerosols has been identified as a potential pathway for cirrus cloud formation. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. While solid ammonium sulfate is an efficient depositional ice nucleus, the role of organics remains largely uncertain. I will discuss recent experiments in our group examining ice nucleation one particle at a time using Raman microscopy. We will probe ice nucleation at low upper tropospheric temperatures on mixed particles containing organics with ammonium sulfate. Raman mapping will be used to probe the composition, phase and structure of the mixed particles. Ice nucleation experiments reveal that at low temperatures, some organic containing particles nucleate ice on the outside while others nucleate ice from the particle interior.
Tuesday, July 17, 2012
Professor Nathalie Mahowald
Aerosol indirect effect on biogeochemistry and climate
The net effect of anthropogenic aerosols on climate is usually considered the sum of the direct radiative effect of anthropogenic aerosols, plus the indirect effect of these aerosols through aerosol-cloud interactions. However, an additional impact of aerosols on a longer time scale is their indirect effect on climate through biogeochemical feedbacks, largely due to changes in the atmospheric concentration of CO2. Aerosols can affect land and ocean biogeochemical cycles by physical forcing or by adding nutrients and pollutants to ecosystems. The net biogeochemical effect of aerosols is estimated to be equivalent to a radiative forcing of –0.5 +/- 0.4 watts per square meter, which suggests that reaching lower carbon targets will be even costlier than previously estimated.
Tuesday, June 26, 2012
Professor Jean-Francois Doussin
University of Paris-East at Creteil (UPEC)
Interuniversitary Laboratory of Atmospheric Systems
Experimental simulation of the secondary aerosol production and ageing from the photo-oxydation of biogenic species
Secondary organic aerosols account for the majority of organic aerosols and play an important role in climate on both the global scale and regional scale. While significant progress has been made on the understanding of SOA formation, the transformations it undergoes during its atmospheric transit are still far from being understood. At the University of Paris East (France), a new indoor atmospheric simulation chamber has been built and its physical characteristics make it particularly well-suited to study SOA ageing processes involving oxidant, sunlight or clouds and their links with aerosol properties. In this talk, a brief description of this new tool, its analytical environment and its capabilities will be given. Then, results on on-going research involving biogenic species (such as a-pinene and isoprene) will be presented. In particular, results about ageing processes at the molecular level and their impact on aerosol properties as well as identification of field tracers for aged SOA will be shown.
Monday, May 14, 2012
Lucy Carpenter, U York, UK
Oxygenated volatile organic compounds (OVOCs) in the remote marine troposphere: Results from the Cape Verde Atmospheric Observatory (CVAO)
Oxygenated volatile organic compounds (OVOCs) in the atmosphere are precursors to peroxy acetyl nitrate (PAN), affect the tropospheric ozone budget, and in the remote marine environment represent a significant sink of the hydroxyl radical (OH). The sparse observational database for these compounds, particularly in the tropics, contributes to a high uncertainty in their emissions and atmospheric significance. Here we show multi-annual measurements of acetone, methanol and acetaldehyde in the remote marine boundary layer made at the Cape Verde Atmospheric Observatory (CVAO) (16,848°N, 24.871°W), a subtropical marine boundary layer global GAW station situated on the island of São Vicente. Simulations of OVOCs at Cape Verde using the CAM-Chem global chemical transport model are markedly different from the observations in both concentration and variability and we explore reasons for this including oceanic and terrestrial primary and/or secondary OVOC sources. Finally, preliminary isoprene data from Cape Verde is discussed in the light of recent suggestions that marine isoprene emissions could contribute significantly to the sub-micron OC fraction of marine aerosol in the tropics.
Monday, May 7, 2012
Fullbright Scholar & NSF International Research Fellow, National University of Mongolia and CIRES, Univ. of Colorado-Boulder
The story behind an upcoming field campaign in Ulaanbaatar, Mongolia – one of the world’s most PM-polluted cities
Abstract: Mongolia’s capital city of Ulaanbaatar, where wintertime daily mean PM10 concentrations can be measured in milligrams and black carbon (BC) concentrations in micrograms, contains some of the world’s most polluted air. Yet the remote city of 1.3 million people, isolated from other major anthropogenic PM sources, is severely understudied in the atmospheric science literature.
This seminar will present the story of Ulaanbaatar’s current air pollution crisis, as well as describe current and upcoming mitigation efforts, which may provide a novel and temporary opportunity to observe the effect of relatively fast PM/BC reduction on regional climate. It will also describe an upcoming year-long field campaign designed to help fill the current information-gap on Ulaanbaatar air pollution, and provide a better foundation for future studies. Lastly, the seminar will discuss opportunities in which others can get involved with both the scientific and outreach components of this project.
Monday, April 30, 2012
The Role of Organic Species on the Ice Nucleation Capabilities of Atmospheric Aerosol
Depositional ice nucleation on atmospheric aerosols has been identified as a potential pathway for cirrus cloud formation. Upper tropospheric aerosols as well as sub-visible cirrus residues are known to be enhanced in both sulfates and organics. While ammonium sulfate is known to be an efficient depositional ice nucleus, the role of organics remains largely uncertain. To explore this role, we used a Knudsen cell flow reactor and Raman microscopy to study the ice nucleation efficacy of crystalline organic films and ammonium sulfate particles coated by liquid or glassy organics respectively. In the Knudsen cell studies, it was found that the ice nucleation efficiency of a series of monocarboxylic acids films was dependent on their O:C ratio. For the Raman experiments, we find that if the organic coatings are liquid, water vapor diffuses through the shell and ice nucleates on the ammonium sulfate core. Here, the organics minimally affect the ice nucleation efficiency of ammonium sulfate. In contrast, if the coatings become glassy, ice instead nucleates on the organic shell. These glassy coatings can alter the ice nucleation efficiency of ammonium sulfate.
Monday, April 23, 2012
Known and Unexplored Organic Constituents in the Earth’s Atmosphere: Instrument Development to Enhance Exploration
Allen Goldstein, Professor, Department of Environmental Science, Policy, and Management and Department of Civil and Environmental Engineering, University of California at Berkeley, USA
A substantial fraction of the atmospheric organic chemicals in both gas and particle phases have not been, or have very rarely been, directly measured. Even though our knowledge of them is limited, these compounds clearly influence the reactive chemistry of the atmosphere and the secondary formation, transformation, and likely the climate impact of aerosols. A continuing challenge in the coming decade of atmospheric chemistry and aerosol research will be to elucidate the sources, structure, chemistry, and fate of these clearly ubiquitous yet poorly constrained organic atmospheric constituents. Critical questions include: What atmospheric organic compounds do we know about and understand? What organic compounds are present as gases and in aerosols? What evidence exists for additional organic compounds in the atmosphere? How well do we understand the transformations and fate of atmospheric organics?
The complex chemical composition of atmospheric aerosols, particularly the organic carbon portion, presents unique measurement challenges. We developed the Thermal Desorption Aerosol Gas chromatograph (TAG) system for hourly in-situ speciation of a wide range of primary and secondary organic compounds in aerosols. This instrument combines a particle collector with thermal desorption followed by gas chromatography and mass spectrometric detection to provide separation, identification, and quantification of organic constituents at the molecular level. Observed compounds include alkanes, aldehydes, ketones, PAHs, monocarboxylic acids, and many more. The hourly time resolution measurements provided by TAG capture dynamic and frequent changes in aerosol composition. We have incorporated a two-dimensional chromatography (GC×GC) capability into TAG with a time of flight (TOF) MS detector. Two-dimensional chromatography provides two types of compound separation, most typically by volatility and polarity using two columns with different stationary phases connected in series separated by a modulator. The modulator periodically traps analytes eluting from the first column, and injects fractions of this effluent onto the second column in the form of narrow pulses providing additional separation for co-eluting peaks. The approach is especially useful for distinguishing polar compounds that would otherwise be buried in the unresolved complex mixture (UCM). We are developing a semivolatile collection system that allows simultaneous measurement of chemically specific semivolatile organics in the gas and particle phases, enabling in-situ analysis of speciated organic partitioning in the real atmosphere. We have also developed and deployed a combined TAG-AMS (Aerosol Mass Spectrometer) instrument for simultaneous measurements of the total and speciated aerosol composition. This talk will review our recent developments (TAG, 2DTAG, SVTAG, TAG-AMS), and present new observations of speciated semi-volatile separations between the gas and particle phases, 2DTAG and TAG-AMS observations in ambient air and controlled chamber source oxidation studies. New experiments using soft ionization techniques to more fully separate the UCM and to identify more of the organic species in aerosols will also be presented.
Monday, April 9, 2012
Airborne MAX-DOAS for measurement of atmospheric trace gases
We have developed a new motion-stabilized scanning airborne multi-axis differential absorption spectroscopy (CU AMAX-DOAS) instrument to retrieve column and profile information of trace gases like NO2, HCHO, CHOCHO, IO, BrO, O4 and aerosol extinction coefficient. Column observations of reactive trace gases provide means to bridge spatial scales between ground-based measurements, and satellite observations, and enable a more direct comparison with atmospheric models for improving emission inventories. This instrument was deployed aboard the NOAA Optical Remote Sensing Twin Otter Research Aircraft during the CalNex 2010 and CARES field campaigns. A total of 52 flights (48 research + 4 transfer flights) were carried out in California between May 19 and July 19, 2010. The focus of this deployment is to map the horizontal and vertical distribution of NO2, HCHO, CHOCHO and O4.
Here we describe the CU AMAX-DOAS instrument, give an overview of the profile retrieval algorithm, and present some results from the CalNex and CARES campaigns. Comparison of measured NO2 vertical columns with CMAQ and WRF-Chem model simulation results will also be presented. Comparisons show strong evidence for decreasing NOx emissions to be widespread in California.
Monday, April 2, 2012
Selection of DNA Aptamers That Would Improve Diagnostic Tests for Tuberculosis
Despite the drastic decline in tuberculosis-related mortality due to the development of a vaccine and the discovery of effective anti-mycobacterial antibiotics during the middle part of the twentieth century, there has been a resurgence of the disease since the 1980’s primarily due to the advent of HIV/AIDS and drug-resistant Mycobacterium tuberculosis strains. The need for improved diagnostic tests that are capable of greater specificity, sensitivity, and rapidity than the current tests is apparent and such tests would contribute significantly to the number of lives saved annually. A DNA aptamer-based biosensor has the potential to meet these challenges; aptamers have proven to have similar dissociation constants to antibodies but provide additional benefits such as increased stability, ease of synthesis and a greater amenability to labeling. The SELEX process will be used to selectively evolve DNA aptamers that bind specifically to antigens particular to Mycobacterium tuberculosis. Aptamers discovered in this way may be used to selectively remove the mycobacterium or antigen from a biological matrix, as well as serve as the detection molecule via conjugation with a reporter in a similar fashion as that of a sandwich-ELISA test.
Monday, March 5, 2012
Texas A&M University
Chemical Transformations of Atmospheric Aerosols and Their Cloud-Nucleating Abilities
Emissions of biogenic volatile organic compounds (VOCs) lead to formation of secondary organic aerosol, contributing to a major fraction of the global tropospheric aerosol loading. The extent to which VOC oxidation products condense onto preexisting primary aerosols and modify their cloud-nucleating properties, however, remain highly uncertain. In chamber studies we show that water-soluble organic acids produced from the reaction between α-pinene and ozone rapidly accumulate onto preexisting soot particles. In less than 30 minutes, initially hydrophobic aerosols are converted to aerosols containing a mass fraction of 80-90% organics which activate efficiently as cloud condensation nuclei under representative atmospheric conditions. Our results imply that the microphysical properties of aerosols present in continental air masses are largely controlled by the composition and thickness of coatings (~30 nm in 30 minutes) formed during aerosol aging processes, rather than by the size or composition of original primary particles. In addition, chemical changes in aerosols impact their ice nucleating ability. Our results suggest that atmospheric models underestimate the impacts of chemical transformations of aerosols leading to inaccurate predictions of the indirect effects of aerosols on climate.
Monday, Feb. 20, 2012
Informal Seminar by Anna Wonaschuetz, University of Arizona (Group of Armin Sooroshian)
Measurements of Aerosol-Cloud Interactions
Ekeley S274, Monday Feb 20 @ noon
In this talk, I will present a brief tour of recent studies related to organic aerosols and cloud-aerosol interactions. The impact of shallow cumulus clouds on the vertical distribution of aerosol properties is investigated with the help of an airborne data set from the 2006 Gulf of Mexico Atmospheric Composition and Climate Study (GoMACCS). Vertical profiles of aerosol volume concentrations and chemical composition (in particular organics, sulfate and oxalate) give evidence of aerosol re-distribution from near the surface into high altitudes. I will also show first results of aerosol hygroscopicity in connection with measurements of WSOC and AMS chemical composition from last summer's Eastern Pacific Aerosol and Cloud Experiment (E-PEACE) field campaign and give a brief summary of two regional aerosol studies in the Los Angeles Basin and the deserts of Southern Arizona.
Monday, Feb. 13, 2012
Susan Doughty, Ph.D., J.D.
Greenlee Sullivan P.C., Intellectual Property Law
IP:50 Intellectual Property in 50 Minutes or Less
It is important for everyone to have an awareness of Intellectual Property (IP) since the legal and financial stakes for missteps are potentially serious and costly. A summary of the types of Intellectual Property protection available as well as a case-study on the intersection of IP with University researchers will be provided.
Tuesday, Jan. 17, 2012
Center for Atmospheric Particle Studies, Carnegie Mellon University
Linking tailpipe to ambient: Quantifying the contribution of motor vehicle emissions to ambient fine particulate matter concentrations
Motor vehicles are an important source of air pollution in urban environments. Although tailpipe emission standards have become progressively tighter over the past few decades, this approach has not achieved the expected air quality benefits. To investigate the contribution of motor vehicle emissions to ambient fine particulate matter, we have conducted a series of smog chamber studies of varying complexity from individual compounds to actual vehicle emissions. The results reveal a dynamic picture in which fine particulate matter formed in the atmosphere dramatically exceeds the direct particle emissions, especially for low emitting sources. The talk concludes with some comparisons to ambient data from recent field studies and a discussion of the implications of these recent findings on human exposures and the design of regulations to control pollutant emissions.
Allen Robinson: Dr. Allen Robinson is a Professor in the Departments of Mechanical Engineering and Engineering and Public Policy at Carnegie Mellon University. His research examines the impact of emissions from combustion systems on urban, regional and global air quality. He received his Ph.D. from the University of California at Berkeley in Mechanical Engineering in 1996 and his B.S. in Civil Engineering from Stanford University in 1990. He was awarded the Carnegie Institute of Technology Outstanding Research Award in 2010, the Ahrens Career Development Chair in Mechanical Engineering in 2005 and the George Tallman Ladd Outstanding Young Faculty Award in 2000.
Friday, Jan. 13, 2012
Prof. Paul Ziemann, University of California-Riverside
Comprehensive Studies of the Chemistry of Aerosol Formation from Alkane Oxidation
Much of what is currently understood about the chemical and physical processes involved in the atmospheric oxidation of organic gases and particles and the formation of secondary organic aerosol (SOA) has been obtained from experiments carried out in environmental (smog) chambers. Achieving a level of understanding from such studies that is sufficient for extrapolating results to the atmosphere and for developing accurate models of SOA formation requires the acquisition of detailed information on a variety of gas and particle properties and processes, such as gas and particle phase reaction kinetics, gas and particle composition, particle phase, compound vapor pressures, and gas-particle-wall interactions. Obtaining such data is a challenge, but in this talk I will show results of studies carried out in our laboratory on the OH radical-initiated reactions of alkanes that are approaching this goal. I will demonstrate that by using a diverse array of measurement techniques including mass spectrometry, gas and liquid chromatography, spectrophotometry (with and without compound derivatization), traditional elemental analysis, pycnometry, temperature-programmed thermal desorption, and scanning mobility particle sizing it is possible to develop quantitative chemical reaction mechanisms of organic gas and aerosol chemistry and models of SOA formation. Doing so, however, requires a more comprehensive approach to chamber studies that attempts to account more fully for the effects of walls.
Monday, Nov. 28, 2011
Reddy Yatavelli and Harald Stark
Gas and particle-phase organic acids measurement at a forest site using chemical ionization high-resolution time-of-flight mass spectrometry during BEACHON-RoMBAS campaign
Organic acids are important constituents of aerosol particles. We will present preliminary analysis of organic acids in gas and aerosol particles measured in a ponderosa pine forest during July - August 2011 as part of the BEACHON-RoMBAS field campaign. We will also introduce the new measurement technique, based on chemical ionization, high-resolution time-of-flight mass spectrometry, utilizing a micro-orifice volatilization impactor [MOVI-ToF-CIMS], that was used to collect this data. Acetate anion (CH3C(O)O-, 59 Th) was chosen as the reagent ion for detection of organic acids. The high-resolution mass spectra, in combination with the temperature-dependent desorption information, can be used to identify specific compounds and estimate their gas/particle partitioning
Monday, Nov. 14, 2011
Juliane L. Fry
(Reed College, Portland OR; currently on sabbatical at CIRES & NCAR ASP)
Role of organic nitrates in secondary organic aerosol (SOA) production in forests
Biogenic hydrocarbons, such as isoprene (C5), monoterpenes (C10) and sesquiterpenes (C15), react rapidly with nitrate radical (NO3) to form low-volatility products. We hypothesize therefore that nitrate oxidation may be an important source of secondary organic aerosol in pollution-impacted forest environments. In this talk I will present new data from the BEACHON-RoMBAS field campaign at the Manitou Forest Observatory in the Colorado front range (July/August 2011) relevant to this hypothesis. I will also describe a set of experiments underway as a collaborative project with NCAR’s Atmospheric Chemistry Division and NOAA’s Chemical Sciences Division to explore nitrate-initiated aerosol formation in laboratory chamber and flow tube experiments.
Monday, Nov. 7, 2011
Nighttime chemistry: Field measurements N2O5 uptake and ClNO2 production
Nighttime chemistry accounts for up to half of the NOx removal from the atmosphere and produces atomic chlorine in the early morning through photolysis of ClNO2. NOx is removed through the production and heterogeneous loss of N2O5. The heterogeneous loss of N2O5 typically produces nitric acid which is removed through deposition. However, it has recently been discovered that in the presence of aerosol chloride, the N2O5 uptake produces ClNO2. The rate N2O5 heterogeneous loss been the subject of several laboratory studies; however, it has rarely been studied using ambient measurements. In this work, N2O5 uptake coefficients are determined from ambient wintertime measurements at the BAO tower in Erie, CO. The uptake coefficients are determined using an iterative box model. These uptake coefficients were found to be anti-correlated with the nitrate fraction of aerosol confirming suppression of uptake by aerosol nitrate. Additionally, a plume of chloride was observed in measurements of aerosol chloride, HCl and ClNO2. The N2O5 uptake coefficient was enhanced in this plume due to the competition between aerosol chloride and nitrate to react with N2O5.
Monday, Oct. 17, 2011
Isotopic Substitution in the Atmosphere and Solar Nebula: Cavity Ring-Down Spectroscopy of CO2 and VUV Photodissociation of CO
Cavity ring-down spectroscopy (CRDS) is an ultra-sensitive spectroscopic technique capable of detecting trace gases in the atmosphere. In the Mark Thiemens group at UC-San Diego, a CRDS instrument was developed for the potential application of source apportionment of CO2 based on its isotopic fingerprint, which is an indicator of the chemical/physical processes the molecule has undergone. The theory behind and experimental design of the instrument is described here. Also, the oxygen isotope effect dominated by VUV photodissociation of CO, its implications for CO photolysis in the solar nebula, and the experimental test of the CO self-shielding theory is briefly discussed.
Temporal Dynamics and Sources of Particle Types in Milwaukee, WI Studied with Single-Particle Mass Spectrometry
Industrial processes and combustion sources release aerosols into the atmosphere that often contain components that are harmful to human health and the environment. In order to understand the sources and dynamics of these aerosol emissions, single-particle mass spectra of ambient aerosols were collected in Milwaukee, Wisconsin using ATOFMS during the summer of 2010. The ATOFMS data provided temporal trends of particulate metals, which can be correlated with wind direction and local source information to pinpoint their origins. Additional insight was gained into the particle emissions and dynamics in the local area by looking at the temporal behavior of particle classes.
Monday, Oct. 3, 2011
Margaret A. Tolbert
Importance of aerosol mixing state for ice nucleating efficiency: combined laboratory and field study
Cirrus clouds composed of water ice are ubiquitous in the tropical tropopause region and play a major role in the Earth’s climate. Any changes to cirrus abundance due to natural or anthropogenic influences must be considered to evaluate future climate change. To understand cirrus cloud formation, it is necessary to determine the factors that control ice nucleation. In this work we have used optical microscopy coupled with Raman spectroscopy to examine water uptake, phase changes and ice nucleation on individual aerosol particles that have been impacted onto a hydrophobic surface. Studies are performed on both laboratory-generated particles of known composition and field-collected particles of unknown composition. Raman mapping experiments provide insight into the mixing state of the various components within single ice-nucleating particles. Results show that although overall chemical composition is important for ice nucleation, particle mixing state must be examined as well.
Rainer M. Volkamer
Oceans, Atmospheric chemistry, and Climate: Novel processes at the air-sea interface
The Volkamer group develops optical spectroscopic instruments for use in laboratory experiments, and field studies to measure reactive trace gases and radicals that are relevant to tropospheric ozone, mercury cyling, and the formation of secondary organic aerosol (SOA). This talk gives an overview about group activities in the recent past and near future. The TORERO field experiment will study the Tropical Ocean Troposphere Exchange of Reactive halogen species and Oxygenated VOC by means of a comprehensive chemical payload of instruments centered around the CU Airborne Multi-AXis DOAS instrument aboard the NSF/NCAR GV aircraft in the area of Gallapagos Islands. It combines aircraft, ship and island based measurements, to probe chemical gases that form by destroying heat trapping ozone and can form new aerosols that cool climate. The group also participates in the Ganges Valley Aerosol Experiment (GVAX) in India, deploying the innovative CU Cavity Enhanced DOAS instrument, and a novel 2D scanning ground-based MAX-DOAS instrument. Future applications at the planned simulation chamber facility as part of the Center for Atmospheric Chemistry are briefly discussed.
Monday, Sep. 19, 2011
INHALABLE DRY POWDER AEROSOLS OF VACCINES AND ANTIBIOTICS
Dry powder aerosol inhalable vaccines are generally inherently more stable than liquid injected vaccines, and they can be administered through the moist respiratory tract along the same mucosal pathway used when wild-type virus infects a patient (PNAS, Jan. 31, 2011). Using unit dose high barrier packaging, there is no "vaccine wastage," which consumes about 40 % of all liquid measles vaccines worldwide, after multidose vaccines are reconstituted with water for injection. Eliminating needles also eliminates accidental needle sticks and the cost of sharps disposal. Because the large surface area of the alveoli of the subject is moist and dissolves the myo-inositol sugar-stabilized rapidly, there is no need to purify and carry water for injection into the field in developing country vaccine campaigns. With high-barrier individually sealed blister packs, contamination can be reduced, and shelf-life increased to 4 years. We are planning a joint study with Doctors Without Borders.
Jose L. Jimenez
Organic Aerosol Sources and Processing in the Atmosphere
Organic aerosols (OA) account for about 1/2 of the submicron particle mass in the atmosphere, but their sources, sinks, and evolution are poorly understood. OA is comprised of primary OA (emitted in the particle phase) and secondary OA (formed from chemical reactions of gas-phase species). In this talk I will summarize research in OA by our group over the last year, including a summary of the recent CalNex-LA and BEACHON-RoMBAS field projects in Pasadena (CA) and Woodland Springs (CO) respectively, direct measurements of the SOA formation and photochemical evolution of ambient air and collaborative work with modelers to constrain the OA budget. I will also discuss our new MOVI-CIMS instrument which allows molecular-level analysis of OA with high sensitivity and mass resolution and some first results from BEACHON-RoMBAS. Finally, I will introduce future field projects in India, Thailand, Southeast US, and the Amazon, and the outlook for the new smog chamber facility in Cristol Bldg.
Monday, August 29, 2011
Thomas J. Wenzel
Chiral Receptor Compounds as Enantioselective NMR Shift Reagents and Catalysts for Curricular Reform
The use of crown ethers, calixresorcinarenes and ionic cyclodextrin derivatives as enantioselective NMR shift reagents will be described. The cyclodextrins and calixresorcinarenes are unusual because they are water-soluble reagents. A crown ether system that is useful for the analysis of secondary amines will be described. The beneficial learning that occurs when undergraduates conduct research was a major factor in causing me to restructure the way I teach my courses. The use of collaborative in-class learning activities and semester-long laboratory projects will be described, as will efforts to enact similar curricular changes at a consortium of over 20 schools.
Friday, August 19, 2011
Arwa Mustafa, Center for Analysis and Synthesis, Department of Chemistry, Lund University, Lund, Sweden
Formulation of Phytonutrients Micro‐particles using Carbon Dioxide Assisted Particle Formulation Targeting Alzheimer’s disease
Alzheimer’s disease (AD) is the result of a progressive aggregation of ß-amyloid peptide (ß‐AP) leading to the formation of extracellular fibrillar that deposits in selected areas of the brain. Polyphenols are efficient fibril inhibitors in AD by destabilizing beta‐amyloid fibrils. Our research aims to develop a drug carrier system that targets the brain via the nasal route to improve the treatment of Alzheimer’s disease (AD) by formulating well‐defined micron‐sized particles (10‐50µm) using supercritical carbon dioxide technology. Chitosan is a natural polymer that has a great potential for nasal delivery system facilitating the passage of hydrophilic molecules through the nasal mucosa. The technique of choice is the Carbon Dioxide Assisted Nebulization with a Bubble Dryer® (CAN-BD) since chitosan is soluble in water that would facilitate the micronization of oleuropein into chitosan.
Monday, May 23, 2011
Ph.D. Defense, Daniel Bon, CIRES Aud., 23-May-11, 2 pm
Measurement of Atmospheric Volatile Organic Compounds from Urban, Industrial, and Biogenic Soruces by Proton-Transfer Ion-Trap Mass Spectrometry
Volatile organic compounds (VOCs) are released into the atmosphere through a variety of natural and human-related processes. Understanding the atmospheric chemistry of VOCs is critical because of the role VOCs play in air pollution and climate. The diversity of VOCs found the atmosphere challenges even modern analytical methods. The Proton-Transfer-Reaction Ion-Trap Mass Spectrometer (PIT-MS) is a unique instrument for real-time measurement of VOCs in ambient air. In PIT-MS, VOCs are ionized by proton-transfer reactions with hydronium (H3O+) ions, and the product ions are detected by ion trap mass spectrometry. The PIT-MS instrument provides a mass spectrum every 1-10 seconds and has the capability for collision-induced dissociation (CID).
The analytical capabilities of the PIT-MS method are evaluated in this study through measurements of air impacted by different VOC sources: biogenic emissions in a California forest, urban emissions in Mexico City, industrial emissions in Houston, Texas, and emissions from controlled biomass burning experiments at the Fire Sciences Laboratory in Missoula, Montana. Through the use of CID, a gas chromatographic pre-separation method and through measurement comparisons with other instruments, the specificity of PIT-MS with regard to VOCs was studied in detail. These results are invaluable to researchers that use mass spectrometry and proton-transfer reactions with H3O+ ions to ionize VOCs.
Data from the MILAGRO campaign in Mexico City are used to characterize the urban emissions of VOCs. Hydrocarbon emission ratios relative to an inert tracer such as carbon monoxide (CO) are found to be about a factor of 2 larger in Mexico City than in the United States. The Mexico City data are also used for VOC source apportionment by the Positive Matrix Factorization (PMF) method. PMF analysis identifies three major VOC sources in Mexico City: vehicular traffic, liquid propane gas (LPG) usage and chemical formation.
PIT-MS instrument data from the TexAQS 2006 campaign in Houston, Texas are used to evaluate an industrial emissions inventory. The complexity of measured VOCs in industrial plumes is significantly larger than described in the inventory. For many VOCs, emission fluxes inferred from the measurements are significantly higher than in the inventory.
Thursday, May 12, 2011
Prof. Jon Abbatt, Univ. of Toronto
Studies in Multiphase Oxidation Chemistry in the Atmosphere: From Halides to PAHs to SOA
Abstract: Although the kinetics and mechanisms of gas phase reactions in the atmosphere are relatively well defined, the processes that occur via aerosol particles are much less well understood. In particular, a general issue persists of the degree to which condensed phase material in the atmosphere is subject to oxidative processes. Such multiphase chemistry may either occur at the surfaces of particles or films in the atmosphere, or in the bulk phase. This seminar will present three examples of multiphase chemistry, moving from a system for which we feel we understand the kinetics well, i.e. bromide oxidation by ozone in ice and water, to progressively less well understood systems, i.e. PAH heterogeneous reactions and the oxidation of SOA materials by hydroxyl radicals. In the case of SOA oxidation, a combination of experiments are presented using both laboratory surrogates for atmospheric SOA, and experiments with field samples. The potential atmospheric impacts of this work will be presented.
Thursday, April 28, 2011
Thesis defense for Ingrid Ulbrich
Characterization of Positive Matrix Factorization Methods and Their Application to Ambient Aerosol Mass Spectra
Thursday, April 28, 2:30 pm CIRES Auditorium
Atmospheric aerosol has impacts on health, visibility, ecosystems, and climate. The organic component of submicron aerosol is a complex mixture of tens of thousands of compounds, and it is still challenging to quantify the direct sources of organic aerosol. Organic aerosol can also form from a variety of secondary reactions in the atmosphere, which are poorly understood. Real-time instrumental techniques, including the Aerosol Mass Spectrometer (AMS), which can quantitatively measure aerosol composition with high time and size resolution, and some chemical resolution, produce large volumes of data that contain rich information about aerosol sources and processes. This thesis work seeks to extract the underlying information that describes organic aerosol sources and processes by applying factor analytical techniques to organic aerosol datasets from the AMS. We have developed a custom, open-source software tool to compare factorization solutions, their residuals, and tracer-factor correlations. The application of existing mathematical techniques to these new datasets requires careful characterization of the precision in the data and the factorization models' behavior with these specialized datasets. We explore this behavior with synthetic datasets modeled on AMS data. The synthetic data factorization has predictable behaviors when solved with "too many" factors. These behaviors then guide the choice of solution for real aerosol datasets. The factor analyses of real aerosol datasets are useful for identifying aerosol types related to sources (e.g., urban combustion and biomass burning) and secondary atmospheric processes (e.g., semivolatile and low-volatility oxidized organic aerosol). We have also factored three-dimensional datasets of size-resolved aerosol composition data to explore the variability of aerosol size distributions as the aerosol undergoes processing in an urban atmosphere. This study provides evidence that primary particles are coated with condensed secondary aerosol during photochemical processing, shifting the size distribution of the primary particles to larger sizes. Application of these three-dimensional factorization techniques to other complex aerosol composition datasets (e.g., that use thermal desorption or chromatography for further chemical separation) has the potential to yield additional insights about aerosol sources and processes.
Monday, April 25, 2011
Frank N Keutsch Department of Chemistry University of Wisconsin-Madison
Measurements of Tracers of Biogenic Volatile Organic Compound Oxidation in Forests: Implications for Missing Sinks and Sources of the OH Radical
The photochemical oxidation of volatile organic compounds (VOCs) is central to the formation of tropospheric ozone and secondary organic aerosol. Particularly in regions dominated by biogenic VOCs (BVOCs), our understanding of the chemistry of the OH radical, the most important tropospheric oxidant, is limited. In these biogenic regions, modeled OH concentrations are often dramatically lower than measurements, demonstrating unknown OH sources. In addition, measured OH sinks are often substantially larger than can be explained, and the presence of unknown, highly-reactive BVOCs have been proposed to explain this missing sink.
We have developed robust instrumentation for the ultra-sensitive measurement of BVOC oxidation products as tracers of BVOC oxidation by combining spectroscopic techniques that are new for field instrumentation with novel lasers. We propose that glyoxal is ideally suited as tracer of OH-driven BVOC oxidation and present rural measurements of glyoxal. We discuss these measurements within the context of the discrepancy between modeled and measured OH radical concentrations. We also present results from a study using the first formaldehyde flux measurements via eddy correlation obtained during the BEACHON-ROCS 2010 campaign at Manitou Forest. Different scenarios that can explain the unexpectedly large daytime fluxes of formaldehyde out of the forest canopy are discussed with respect to implications for the proposed unknown, highly-reactive BVOCs
Monday, April 18, 2011
Prof. Jesse H. Kroll Assistant Professor Civil and Environmental Engineering and Chemical Engineering MIT
Laboratory studies of the photochemical aging of organic aerosol
The multigenerational oxidative processing (“aging”) of atmospheric organic aerosol is poorly understood, despite its likely influence on particle loadings and properties. In these experiments, n-alkanes are exposed to elevated levels of OH, in order to access the equivalent of several days’ worth of atmospheric oxidation. Measurements of the abundance and oxidation state of particulate organic carbon demonstrate the important role of fragmentation (C-C bond-breaking) reactions as oxidation progresses. Such reactions are highly efficient pathways for the formation of oxidized carbon; however, the corresponding changes to carbon number also tend to offset any decreases in volatility from the addition of functional groups. Thus particulate organics have increasingly smaller carbon numbers as they become more oxidized, with the continual escape of some fraction of the carbon to the gas phase during aging.
Monday, April 11, 2011
The Development of Inhalable Antibiotics for the treatment of TB
The goal of this project is the development of unit-dose, inhalable, antibiotic microparticles for use in primary and combined therapy approaches to treating tuberculosis (TB) and highly drug-resistant strains of Mycobacterium tuberculosis (Mtb) that result in multi drug-resistant (MDR-TB) and extensively drug-resistant TB. Targeted to the alveolar space by merit of high fine particle fractions (FPF) in the < 3.3 µm range, these antibiotic microparticles utilize the same inhalation pathway as Mtb, to deliver antibiotic to protected TB lesions. This study explores strategies of combining microparticles with excipients to improve the fine particle fraction and deliver a larger fraction of antibiotic to the deep lung.
CAN-BD Processed Vaccines, Safer Vaccination in a Breath of Fresh Air
In a modern world where the media and fringe groups seem to be touting the supposed dangers of vaccination, the scientific observations remain that many lives are saved and epidemics prevented through the use of vaccines. In an effort to improve the safety of vaccinations in the developing world the Sievers group is currently researching the production of inhaled, needle-free vaccines. This talk will cover the design of a needle-free dry powder HPV vaccine, collaboration with an overseas vaccine producer (Serum Institute of India) in the production of a needle-free Measles vaccine and tests of uniform activity throughout the particle size ranges of the aforementioned vaccine.
Monday, April 4, 2011
Charles S. Henry Departments of Chemistry, Chemical and Biological Engineering, and School of Biomedical Engineering Colorado State University
Microfluidic Tools for the Analysis of Aerosol Chemistry
Ambient aerosols have significant impacts on both our environment and human health. From an environmental perspective, aerosols are one of the most significant unknowns for predicting the impact of human activity on the earth's climate. From a health perspective, aerosols are known to contribute to a wide range of diseases and cause significant changes in mortality and morbidity, however, the mechanisms for these health effects are not clear. It is clear for both environmental and health effects that knowing chemical composition is important in developing a better understanding of the impact of aerosol. This talk will focus on new microfluidic tools our lab has create to measure the chemical composition of aerosols. Microfluidic devices are attractive as an alternative to traditional aerosol analyzers because they can provide fast measurement times, high sensitivity, are compatible with a range of measurement chemistries, and can be relatively inexpensive. This talk will focus on recent results from our laboratory where microfluidic tools were used to make measurements of key chemical components of aerosols.
Monday, March 28, 2011
Dr. Erika Dawson InDevR Boulder, CO
Translating Academic Research into New Products for Virus Quantification and Identification
This talk will describe my experiences at InDevR during the development of our two existing product lines, the ViroCyt Virus Counter and ampliPHOX Colorimetric Detection Technology. Starting with two separate technologies originally developed at CU, InDevR has advanced the original ideas into two unique instruments that are currently in different stages of development. I will share some recent data comparing the Virus Counter to standard virus quantification methods for applications in bioprocessing and vaccine development. I will also describe how ampliPHOX has been utilized to quickly and inexpensively detect and characterize influenza viruses using the FluChip.
Monday, March 14, 2011
Highly Concentrated Dispersions of Stable Submicron Therapeutic Protein Particles For Subcutaneous Injection
Keith P. Johnston
Dept. Chemical Engineering, Univ. of Texas Austin
Protein and peptide therapeutics address needs in a wide range of diseases including cancer, infectious and inflammatory diseases. Despite their successes, administration of these therapeutics is limited by the lack of efficacious alternatives to intraveneous delivery of the required 100-500 mg doses. Here, we report a novel strategy compatible with subcutaneous injection that preserves IgG activity: aqueous-based, dispersions of submicron particles at 300 mg/ml IgG concentrations with apparent viscosities of below 50 cP. These dispersions may be prepared by generation of IgG particles, formed with thin film freezing (TFF) or a novel rapid spiral wound in-situ freezing technology (SWIFT) that preserve protein stability by limiting the protein’s exposure to liquid/gas and liquid/ ice interfaces. Dispersions of these particles in a solution containing PEG300 and n-methyl-2-pyrrolidone in buffer at the protein isoelectric point restricted protein solubility to <40 mg/ml and prevented complete particle dissolution. The low apparent viscosities of these dispersions result from the low viscosity of the initial solution and the low intrinsic viscosities ([η]). Additionally, antibody stability against denaturation and aggregation (as measured by HPLC SEC and ELISA) was enhanced by low solvation and decreased protein mobility of the solid state. High protein stability and biological activity is maintained upon subcutaneous delivery into mice(Jennifer Maynard laboratory, UT). The ability to form active, highly concentrated dispersions of therapeutic proteins with low viscosities, offers novel opportunities in subcutaneous injection for more effective treatment of disease.
Monday, March 7, 2011
Optical constants of model SOA formed by cloud processing
Aerosols play an important but poorly understood role in affecting the Earth’s climate, and a better understanding of their origins and properties is required. A significant fraction of organic aerosol is composed of large light-absorbing species, but the formation and properties of these species are not well known. Recent work has shown that reactions between small organic molecules in cloud water can form species with chemical and physical properties very similar to the oligomers found in aerosols. We used cavity ring-down aerosol extinction spectroscopy and atomic force microscopy to examine the optical and physical properties of these model aerosols. The effects of these particles on direct radiative forcing were modeled to determine the significance of these particles on climate.
A case study for SOA formation by glyoxal processing in aqueous aerosol in Mexico City
The role of heterogeneous chemistry as a source of Secondary Organic Aerosol (SOA) remains difficult to quantify. SOA is the portion of organic aerosol that forms in the atmosphere as a result of atmospheric transformations. Glyoxal is a building block for SOA formation as a result of heterogeneous chemistry. Measurements from the MCMA-2003 campaign in Mexico City showed that the gas phase glyoxal concentrations were lower by a factor of two to three than predicted by the Master Chemical Mechanism, and that this missing gas phase glyoxal was equivalent to the formation of about 5 μg/m3 of organic aerosol mass over the course of eight hours. Numerous recent laboratory studies have found that glyoxal can form significant amounts of SOA due to uptake, by both dark (equilibrium and irreversible) processes and by rapid photochemical uptake to aerosols. These processes have recently been reviewed, and a model framework has been developed based on these laboratory experiments to numerically describe glyoxal processing in aqueous aerosol particles. Here this model is applied to predict SOA formation due to glyoxal processing in Mexico City. We present an initial case study where the model was constrained with measurements from Mexico City during MCMA 2003 in a first attempt to bridge between laboratory and field observations, and an early assessment of our understanding of the processes and parameters that determine the amount of SOA formed from glyoxal.
Monday, February 14, 2011
Roles of Subvisible Particles in Protein Aggregation Pathways
University of Colorado, Health Sciences Center School of Pharmacy
Typically, protein aggregates are arbitrarily divided in subclasses: 1) soluble aggregates are oligomers that are found in solution and include species ranging in size from dimers to those large enough to elute in the void volume of a size exclusion chromatography (SEC) column; 2) insoluble aggregates are those that can be separated from the native protein and soluble aggregates by centrifugation or filtration; and 3) particles are aggregates that are usually too large to be analyzed by SEC and are at too low of a mass percent to be quantified by mass loss due to filtration or centrifugation. Particles typically are counted for quantification, and the size range examined is from about 1 micron to 125 microns. The connections between all of these species in the aggregation pathways of proteins are poorly understood. However, recent studies in which all three types were quantified during pharmaceutically relevant stresses (e.g., freeze-thawing, agitation and agitation in the presence of silicone oil) have shown that the first detectable aggregate type is subvisible particles. These can be quantified at mass percent far below the limit of detection for loss of monomer. Thus, particle counting provides the most sensitive method to date to observe and quantify protein aggregation. Also, it appears that when there is sufficient mass of aggregate such that insoluble aggregates can be quantified due to loss of monomer, these aggregates are composed of agglomerates of subvisible particles. Therefore, subvisible particles are fundamentally important components on the protein aggregation pathway. Finally, when particles are formed during a unit operation such a filling of vials, the particles can foster enhanced protein aggregation and particle formation during subsequent stress (e.g., agitation after vial filling).
Monday, February 7, 2011
Peter Bernath Department of Chemistry, University of York, Heslington, York, YO10 5DD, UK
An overview of the spectroscopy of the Earth’s atmosphere with the Atmospheric Chemistry Experiment (ACE) satellite will be presented. The primary instrument is a high-resolution infrared Fourier Transform Spectrometer (FTS) operating from 2 to 13 microns that measures the vertical distribution of trace gases, and the meteorological variables of temperature and pressure. Secondary instruments include a UV/Visible spectrometer called MAESTRO and two filtered solar imagers. Although now in its eighth year, the ACE satellite is still operating nominally. Ground-based atmospheric solar absorption spectra recorded with a copy of the ACE-FTS will also be discussed. The analysis of our spectra requires new laboratory measurements as will be illustrated with satellite retrievals of a wide range of organic molecules associated with air pollution.
Monday, January 31, 2011
Segregating Primary Biopolymer Associations with Airborne Particulate Matter: A Sanitary Engineering Perspective on Bioaerosol Traffic in the Atmospheric Environment
Prof. Mark Hernandez, Environmental Engineering, UCB
While generally considered oligotrophic, the atmosphere carries microcellular hallmarks of life – both in primary and weathered forms. In this context, bioaerosols are defined as a generic class of airborne particulate matter comprised either in whole or in part of macromolecular compounds of biological origin. The contribution of the most common primary biopolymers — DNA, lipids, carbohydrates and proteins — to the pool of atmospheric organic carbon remains relatively unknown, as is their potential to weather and participate in secondary aerosol formation. We report here, phylogenetic characterization of atmospheric DNA pools juxtaposed to carbohydrate, proteins and lipids, as normalized by size segregated organic carbon mass.
Monday, November 29, 2010
Ground based FTIR and MAXDOAS column observations of atmospheric trace gases
Carbon monoxide (CO) and Nitrogen dioxide (NO2) are important pollutants in urban agglomerations. Even though surface concentrations of those pollutants have been monitored routinely, the quantification of the total load (vertical column integral of concentration over the boundary layer height) is challenging because surface concentrations may not be representative over height of the boundary layer; the vertical distribution may further be variable. This presentation consists of two parts describing the measurement and retrieval techniques as well as results for CO and NO2 in two very different urban environments, Mexico City and Los Angeles, CA.
The diurnal trend of columnar CO in the boundary layer of Mexico City has been measured during one year with ground-based infrared absorption spectroscopy. Daytime CO total columns are retrieved from measured solar spectra and for the first time, nocturnal CO total columns using moonlight have been retrieved within a megacity. The measurements were taken at the Universidad Nacional Autonoma de Mexico (UNAM) campus located in Mexico City (19.33N, 99.18W, 2260 m.a.s.l.) from October 2007 to October2008 with a Fourier-transform infrared spectrometer (FTIR) at 0.5 cm-1 resolution.
An overview of measurements with a MAXDOAS instrument deployed at the Caltech supersite in Pasadena, CA this year will be presented in the second part of this talk. Validation of real time slant column densities of NO2 will be presented from the period of May to June 2010 in Pasadena, CA as part of CALNEX campaign. Using a geometric approximation NO2 vertical column densities are retrieved. The degree of mixing in the boundary layer is assessed by comparison of the NO2 vertical column densities with NO2 mixing ratios as measured from a cavity enhanced DOAS instrument located on top of Millikan Library, and independent measurements of mixing height by ceilometers.
Monday, November 15, 2010
Isotopic Labeling of Early Earth Haze Analogs
The Faint Young Sun paradox predicts that the surface temperature of the early Earth was below the freezing point of water. A cold Earth is the expected outcome of an atmosphere composed of nitrogen and trace amounts of carbon dioxide coupled with a sun whose intensity was only 70% of its current luminosity. However, a cold Earth contrasts with the geologic record, which suggests that the early Earth was warm and had liquid water on its surface. The paradox can be resolved by adding methane, a strong greenhouse gas, to the weakly warming atmosphere assumed in the paradox. We have shown that atmospheres composed of nitrogen and trace amounts of methane and carbon dioxide will produce a haze when irradiated by light at the Lyman-a wavelength (121.6 nm). Such a haze would have implications for the early climate, as well as for the origin and evolution of life.
Now that the possibility of haze has been demonstrated, some questions remain: What is its composition? How is it made? To answer these questions, we label each of the carbon sources with 13C and use an aerosol mass spectrometer (AMS) to observe the haze fragments generated by electron impact ionization. We aim to use the information generated by the AMS, coupled with isotopic labeling, to elucidate the chemical pathway(s) by which the haze is made. In this talk, we share preliminary results from these experiments, demonstrate the feasibility of the proposed methods in elucidating the pathway(s), and touch on future work.
Monday, November 1, 2010
Levoglucosan, S-Phenylmercapturic Acid, and S-Benzylmercapturic Acid as Urinary Biomarkers of Wood Smoke Exposure
Wood smoke (WS) inhalation is a source of adverse health effects in humans due to its toxic and carcinogenic constituents. Monitoring exposure levels to WS through the use of urinary biomarkers can support epidemiological studies involving the direct health effects of exposure and help evaluate the effectiveness of efforts to limit human exposure in the future. Studies on levoglucosan showed that the diet has too large of an influence on its urinary concentration to conclusively quantify WS exposure. This project focuses on two other potential urinary biomarkers, s-phenylmercapturic acid (SPMA) and s-benzylmercapturic acid (SBMA), that have been previously successful for monitoring environmental tobacco smoke and industrial smoke exposure in humans, and studies their effectiveness in quantifying WS exposure. The hypothesis of this study is that both SPMA and SBMA will be effective biomarkers of WS exposure. To test this hypothesis, methods for the extraction and analysis of these compounds from urine were developed, evaluated and applied to the urine of exposed and control human subjects. The analytical method was found to have a limit of detection of 10ppb and a limit of quantitation of 50 ppb. Analyses of urine from individuals before and after exposure to WS showed quantifiable levels of the markers in 60% of samples, did not reveal a significant increase or decrease in concentrations of biomarkers in post-exposure relative to pre-exposure samples. The results imply that these biomarkers may not be suitable to determine exposure to WS. Additional studies to improve the extraction and detection sensitivity and reproducibility, as well as to monitor urinary levels over longer periods of time pre- and post exposure are needed to conclusively determine the utility of these markers.
A Molecularly Imprinted Polymer as a Sensor for Nicotine
Molecularly imprinted polymers (MIP) have been shown to preferentially bind molecules with specific shape or functional groups. This technology is discussed as it relates to the development of a nicotine sensor. Qualitative results are shown using an Atomic Force Microscope and FTIR spectra, and progress is made towards quantitative analysis using a GC.
Monday, October 25, 2010
Copper Binding by Dissolved Organic Matter using Competitive Ligand Exchange- Solid Phase Extraction and Application to the Biotic Ligand Model
The toxicity of copper to aquatic organisms is dependent on the aqueous copper speciation. The free copper concentration (Cu2+) primarily controls the toxicity of copper to fish due to its adsorption in the gill (a “biotic ligand”). Copper binding by dissolved organic matter plays a significant role in copper speciation and toxicity by reducing the amount of free copper that can bind to the biotic ligand. The biotic ligand model (BLM) is a model that predicts the concentration of free copper as a function of pH, dissolved organic matter concentration, and water hardness. While the model includes dissolved organic matter, there is still much uncertainty as to the correct copper-dissolved organic matter binding constants to include in the model. Much work has been done to measure the conditional stability constants for the copper-dissolved organic matter complex, but the methods used to measure these stability constants have “detection window” limitations that are not always recognized by those incorporating the stability constants into toxicity models. In this study, the competitive ligand exchange-solid phase extraction (CLE-SPE) method was used to measure the stability constants at pH 6.5 and 0.01 ionic strength over a wide range of Cu:dissolved organic matter concentration ratios. A comparison of the CLE-SPE stability constants with those measured by other methods revealed that the most important factor to determine the binding strength is the ratio of Cu:dissolved organic matter concentration, even for dramatically different environmental and experimental conditions. The Cu:dissolved organic matter concentration ratio is important because as the ratio decreases, the binding constant increases due to the heterogeneity of binding sites present in dissolved organic matter. Results obtained from this study can be used in the BLM to more accurately predict the role of dissolved organic matter in copper speciation.
Monday, October 4, 2010
Eddy-covariance measurements with time-of-flight mass spectrometry: A new approach to chemically-resolved organic particle and gas fluxes
Delphine K. Farmer
Although laboratory studies show that biogenic VOCs yield significant secondary organic aerosol, emission of biogenic SOA fluxes has not yet been conclusively observed over forests. Further, while aerosols are known to deposit to forest surfaces, the chemical identity and ecosystem implications of this deposition flux remains undetermined. To better constrain sources and sinks of biogenic SOA, we have developed a new technique to directly measure fluxes of chemically resolved aerosol over forests using the High Resolution Time-of-Flight Aerosol Mass Spectrometer in a new, fast eddy covariance mode. This approach allows us to quantitatively identify both organic and inorganic components, including NH4+ , SO4_2- and NO3- , and has been deployed over both temperate and tropical forests. Results show both upward and downward fluxes of aerosol, including deposition of NH4+ . Differences in direction and magnitude of different chemical components provide insight on aerosol chemistry and potential ecosystem effects. In particular, we observe evidence for rapid formation or growth of biogenic SOA within both temperate and tropical forest canopies.
Aerosol Composition in Los Angeles During the 2010 CalNex Campaign Studied by High Resolution Aerosol Mass Spectrometry
Patrick L. Hayes
Submicron atmospheric aerosols impact climate and human health, but their sources and composition are poorly understood. To address this knowledge gap, high-resolution time-of-flight aerosol mass spectrometry (AMS) and other advanced instrumentation were deployed during the CalNex field campaign in May and June 2010 to characterize the composition of aerosols in the Los Angeles area. Utilizing AMS, the concentrations for both organic and non-refractory inorganic (sulfate, nitrate, ammonium, chloride) submicron aerosols were quantified at the Pasadena ground site 15 km NE of downtown Los Angeles. Nitrate aerosols appear to dominate in the cooler mornings, but their concentration is reduced in the afternoon when organic aerosols (OA) increase and dominate. The diurnal variations in concentration are strongly influenced by vertical dilution from the rising planetary boundary layer in the afternoon. The concentrations of oxygenated OA (OOA), and hydrocarbon-like OA (HOA) are estimated, and it is found that OOA is consistently the largest type of OA present (~75% of the total OA concentration). This result indicates that the air mass over the site has undergone substantial chemical aging. The correlations between OOA and Ox (O3 + NO2) concentrations, as well as between HOA, CO and black carbon concentrations are consistent with previous studies. Ultimately, the goal of this research will be to test the accuracy of recently-proposed SOA models by combining the characterization of SOA with measurements of precursor and oxidant concentrations carried out concurrently during CalNex.
Monday, September 27, 2010
Update on RASEI, Solar Fuels, and Critical Areas of Electrochemical Energy Research
Carl A. Koval
Since 2006, my primary responsibility has been the creation and development of CU-Boulder’s Energy initiative, which became the Renewable and Sustainable Energy Institute (RASEI). The first part of my presentation will be to reflect how RASEI got to where it is and, hopefully, where it is going. The second part will focus on how large-scale solar production of hydrogen is likely to be the first step towards creating a solar fuels industry. Finally, I will briefly describe three critical areas of energy research that the (photo)electrochemistry community needs to address.
Organic Aerosol Sources and Processing in the Atmosphere
Jose L. Jimenez
Organic aerosols (OA) account for about 1/2 of the submicron particle mass in the atmosphere, but their sources, sinks, and evolution are poorly understood. OA is comprised of primary OA (emitted in the particle phase) and secondary OA (formed from chemical reactions of gas-phase species). In this talk I will summarize research in OA by our group over the last year, including a summary of the recent CalNex-LA field project in Pasadena (CA), research on the SOA formation and photochemical evolution of biomass burning emissions, on SOA model/measurement comparisons in different environments, and on collaborative work with global modelers to constraint the global OA budget. I will also discuss upcoming projects including characterization and use of semicontinuous GC-MS and chemical ionization mass spec. to analyze OA, and field projects in the Rocky Mountains, India, and Southeast Asia.
Monday, September 20, 2010
Nanoscale Therapeutics in the Treatment of Multidrug Resistant Pathogens
In the past century, great strides have been made in the design and synthesis of pharmaceutical compounds for the treatment of human disease. Diseases such as breast cancer and chronic mylogenous leukemia, once thought to be completely untreatable, are now survived by a large percentage of patients. However, there is a large number of pressing medical issues related to the use of small-molecule drugs that must be addressed. For example, the emergence of drug-resistant bacterial and viral strains represent significant global medical challenges to overcome in the 21st century. To provide the tools to potentially treat infectious diseases, we have been developing ligand-coated gold nanoparticles as a new paradigm for drug discovery. Our work to date has offered some hope that the gold nanoparticle therapeutic platform may be a promising one in the search for new treatments for viral and bacterial disease. A few examples from our labs are the use of 2.0 nm diameter ligand-coated gold nanoparticles in the prevention of HIV fusion to human cells, and in the growth inhibition of E. coli and methicillin-resistant S. aureus. These results have inspired us to think in new ways about gold nanoparticle-based therapeutic design and the molecular-level design parameters that may influence activity. This talk will discuss some of these considerations.
The First Inhalable Dry Powder Measles Vaccine Entering Clinical Trials
Robert E. Sievers
Ten percent of all pre-school deaths in India are measles-related. We have developed a Measles Vaccine, Dry Powder (MVDP) and PuffHaler® a novel dry powder inhaler for respiratory delivery to overcome the safety and vaccine wastage problems associated with the current injectable vaccine. MVDP was manufactured from bulk liquid, live attenuated, measles vaccine using CAN-BD® to yield a stable, dry powder, with fine particles suitable for aerosolization and delivery to the pulmonary tract by inhalation. This was achieved by substituting myo-inositol for sorbitol as a stabilizing sugar that is less hygroscopic. Contact with water is detrimental to the stability of measles vaccine and the microparticles are reconstituted only when they deposit in the moist surfaces of the respiratory tract. There is no need for purified water to be carried to remote locations. The particles dried by CAN-BD are homogeneous; the vaccine viral activity distribution in the 1 to 5 micron aerodynamic diameter microparticles is the same as the mass distribution, within experimental error. The shelf life is excellent at 2 to 8 °C with only about 0.5 log loss of activity after more than 2 years. At 25 °C, there is approximately 0.8 log loss after 6 months of storage. The immunogenicity and protective efficacy of a primary dose of MVDP delivered was tested in non-anesthetized, free breathing, Rhesus macaques. MVDP induced MV-specific humoral and T-cell responses at least as robust as subcutaneous measles vaccine and completely protected macaques from infection with wild type measles virus without adverse effects. Phase I clinical trials are now scheduled.
Monday, September 13, 2010
Sulfur Particles on Early Earth
Margaret A Tolbert
Understanding the atmosphere of the early Earth during the Archean, the period of time approximately 4 – 2.45 billion years ago, is an important part of understanding the conditions under which life originated and developed. While the atmospheric composition in highly uncertain during this time, it is likely that volcanic activity released sulfur dioxide into the air. Because of the lack of oxygen on the early Earth, the atmospheric chemistry of sulfur is expected to be quite different than on present day Earth. It has been suggested that atmospheric reactions in a reducing atmosphere could favor S8 particles over sulfuric acid particles. Here we use aerosol mass spectrometry to probe the chemical composition of particles formed from reactions of sulfur dioxide under a range of atmospheric conditions. Implications for the early Earth are discussed.
A heterogeneous open ocean source for glyoxal and iodine oxide
The climate relevance of biologically active ocean upwelling regions has primarily been studied in terms of the air-sea partitioning of long-lived greenhouse gases (e.g., CO2, CH4, N2O etc), and the release of the reactive gas DMS, which can form aerosols as a result of atmospheric transformations. Considerably less attention has been paid to open ocean sources of other reactive gases that, like DMS, can form aerosols. Such molecules are glyoxal (CHOCHO) and iodine oxide (IO). Glyoxal is an indicator for oxidative hydrocarbon chemistry, and a building block for secondary organic aerosol (SOA). SOA modifies the hygroscopic properties of organic aerosols, and potentially also adds to the growth of small particles to sizes that can more easily activate to form cloud droplets. Iodine oxide (IO) can nucleate new particles, and/or add to the growth of pre-existing particles. Due to the very high solubility of the glyoxal molecule, concentrations in excess of 100ppt over the open ocean like we found over the Pacific Ocean require an airborne source mechanism (Sinreich et al., 2010). We have investigated the source mechanism further during a ship campaign in 2009, as well as a first research flight aboard the NSF/NCAR GV research aircraft (HIAPER). Both campaigns give clues about the sources of both gases over the remote tropical Pacific Ocean, and reveal a surprising impact on the composition of the free troposphere.
Tuesday, April 27, 2010
Laboratory Studies of Titan Tholins
Saturn’s moon Titan is enshrouded in a thick orange haze. A similar haze may have formed on the early Earth and provided the organic compounds necessary for the emergence of life. This talk will present results from several laboratory studies focusing on the manipulation of Titan aerosols, also known as tholins, for chemical analysis and simulation of prebiotic processing. Analysis techniques include nuclear magnetic resonance (NMR) and sizing by the scanning mobility particle sizer (SMPS). This will be followed by preliminary results from in-situ analysis by the Aerodyne quadrupole aerosol mass spectrometer (Q-AMS) of tholins formed at a range of pressures.
Tuesday, April 13, 2010
DOAS Measurements of Halogen Oxides
Halogens species are of outmost importance to the atmosphere due to their potential to destroy ozone and the DOAS (differential optical absorption spectroscopy) method is a powerful tool to measure halogen oxides like IO, BrO, but also OClO. After a brief introduction to the longpath-DOAS and multi-axes-DOAS techniques, this talk will present results from several field studies focusing mainly on the observations of iodine and bromine oxides and their impact on the marine boundary layer. This will be followed by a brief excursion to the stratosphere and the chlorine chemistry of the polar ozone hole. The third part of the talk will give an outlook on the future deployment of an airborne multi-axis (AMAX) DOAS instrument in the CalNex campaign in California this summer.
Tuesday, April 6, 2010
Single Particle Studies of Aerosol Hygroscopicity, Aging and Mass Accommodation
Professor Jonathan P. Reid, School of Chemistry, University of Bristol, UK
Studies of the processes that govern the physical and chemical transformation of aerosol particles are crucial for improving our understanding of the properties of atmospheric aerosol. In particular, the equilibrium state is governed by hygroscopicity, the vapour pressures of semi-volatile organic components, and mixing state. Aerosol optical tweezers can provide a method for isolating single particles, or multiple particles of distinct composition for comparison. When combined with cavity enhanced Raman spectroscopy, particle size, composition and morphology can be characterised in detail. We will first examine how such an approach can allow an examination of the equilibrium state of aerosol. Measurements of the chemical aging of mixed component aerosol (oleic acid/sodium chloride/water) by ozone will then be reported. Finally, a novel approach for probing the kinetics of the mass transfer accompanying condensation or evaporation of water will be described and first measurements reported.
Tuesday, March 30, 2010
Development and Application of a Metastable Atom Bombardment (MAB) Source for Penning Ionization Time-of-Flight Aerosol Mass Spectrometry
The Aerodyne time-of-flight aerosol mass spectrometer (ToF-AMS) utilizes thermal vaporization followed by electron ionization (EI) to convert aerosol components to gas-phase ions. The method enables quantification of chemical classes, but the extensive fragmentation caused by EI limits the specificity of both chemical analysis and source identification by factor analysis. To better identify the molecular components of aerosols, we have constructed a metastable atom bombardment (MAB) ionization source that can be interfaced to standard ToF-AMS hardware. A beam of metastable rare gas atoms is produced by a low-voltage DC discharge and focused toward the vaporization plume, yielding Penning Ionization of the analyte molecules. By changing gases, the excited energies of the metastables can be adjusted between 20.61 eV (He) and 9.92 eV (Kr). Source parameters, including pressures, current, geometry, and materials, were optimized for He, Ar, and Kr. Instrument sensitivity and induced fragmentation was characterized for each using lab-generated oleic acid particles. The demonstrated sensitivities are 0.1% of EI (3% of the SNR of EI in the V-mode, comparable to the Q-AMS SNR), which is sufficient for ambient monitoring. A metastable flux of 2.6e14 sr-1sec-1 has been achieved. The MAB-AMS has been deployed to the FLAME-3 campaign at the USDA Fire Sciences Laboratory in Missoula, MT, and used to sample smoke from open burning of different biomass samples.
Tuesday, March 16, 2010
Hugh Coe, Prof. of Atmospheric Composition, University of Manchester, UK
Title: "Secondary Aerosol Composition and Properties: A contrast between European Pollution and Tropical Biogenic Environments"
Abstract: This talk will describe a number of recent studies of secondary aerosol properties and processes in two contrasting environments - European pollution, sampled during the EUCAARI Intensive study in May 2008, and a clean tropical biogenic environment, sampled during the Oxidants and Particle Production Potential (OP3) study in Borneo, also in 2008. The EUCAARI project aims to advance our understanding of climate and air quality by integrating laboratory studies, both short and long term field investigations, satellite data, and modeling at regional and global scales. I will present airborne observations taken during an intensive study to provide a local and regional scale overview of the general composition trends of atmospheric aerosol over northern Europe.
The time dependent measurements obtained by aerosol mass spectrometry enable the chemical transformation time scales of aerosol material to be explored. In particular, factor analyses of the observed organic mass spectral fingerprint demonstrates the continuum nature of chemical processing. Ammonium nitrate is an important aerosol component in NW Europe. It exists in a temperature dependent equilibrium which favours particulate formation in the moist, cool upper portion of the boundary layer. We have shown that this results in aerosol optical depths inferred from ground based measurements are biased low by up to 50% by comparison with AERONET, aircraft measurements, and lidar data during periods of high AOD in anticyclonic conditions. The ubiquitous nature of black carbon (BC) was also demonstrated and how this is processed by secondary particulate will be shown using single particle soot photometry. These topics will all be explored and comparison with global model studies will also be discussed. In contrast, tropical environemnts are dominated by transport of aerosol into the region, by primary production of biological material in the coarse mode aerosol or by secondary organic aerosol produced within the region by photochemical oxidation of precursors. These will presented and the properties of secondary organic material compared with other tropical sites and with global models.
TUESDAY, March 9, 2010
Title: Experimental simulation of Titan’s atmosphere by a radio-frequency plasma
Titan is the biggest satellite of Saturne (about half the Earth). Its dense atmosphere of 1.5 bar at the surface is mainly composed of nitrogen and methane. So Titan is considered as an interesting analog of a frozen primitive Earth. Despite the very low temperature, between 100 and 200 K, atmospheric layers undergo efficient reaction chains, initiated by the solar flux and the Saturn magnetospheric electrons. Complex organic matter made of nitrogenated hydrocarbons is produced into the gaseous phase leading to a brownish photochemical fog surrounding the whole satellite.
Several techniques have been developed to simulate lab analogs, called tholins, of Titan’s haze. Most efficient methods presently known involve plasma techniques. Such a plasma device, named PAMPRE, has been developed in LATMOS, using a RF plasma discharge (13.6 MHz) in a stationary flux of nitrogen and methane gaz mixture, at various temperature and pressure conditions. Recent results will be presented concerning in situ mass spectrometry analysis of the gaseous phase and ex-situ chemical and morphological analysis of the tholins.
TUESDAY, March 2, 2010
Dry powder formulation development for nasal vaccination
Regina Westmeier, Department of Pharmaceutics and Biopharmaceutics, Christian Albrecht University, Kiel, Germany
I will briefly talk about some aspects of the mucosal immune system, which are important for the nasal vaccination strategy. I will then focus on the nose as delivery location, introduce a nasal cast model for the determination of formulation deposition in the different parts of the nose and show some delivery devices I have been characterizing. Further on I will shortly review the vaccine delivery systems described in literature and will then talk about our formulation strategies. Besides I will introduce a rapid in vitro test to assess the respiratory toxicity of both excipients and complete formulations.
TUESDAY, February 16, 2010
Observations of iodine oxide and reactive gaseous mercury at a coastal site in Pensacola, FL
An increasing body of evidence suggests that atmospheric halogens, marked largely by the presence of BrO and IO, are ubiquitous components of the lower troposphere in coastal and oceanic areas. The role of halogen chemistry in mercury oxidation in coastal regions remains unknown. Simulations of atmospheric mercury oxidation suggest that chemistry initiated by atomic Br may have been underestimated. Synergistic effects of the iodine compounds can be expected and little is known about the possible direct role I atoms may play to oxidize mercury. Finally, other reactive trace gases, such as CH2O and C2H2O2, can suppress the oxidation of Hg by converting bromine-radicals into chemically inert reservoir species. Here we present data from several months of MAX-DOAS measurements of halogen oxides, O4, CH2O and C2H2O2 in parallel with measurements of speciated mercury (Hg0, Hg2+) that are currently being conducted along the U.S. Gulf Coast.
TUESDAY, February 9, 2010
Light Emitting Diode Cavity Enhanced Differential Optical Absorption Spectroscopy (LED-CE-DOAS): a novel technique for monitoring atmospheric trace gases
Ryan Thalman and Rainer Volkamer
The combination of Cavity Enhanced Absorption Spectroscopy (CEAS) with broad-band light sources (e.g. Light-Emitting Diodes, LEDs) lends itself to the application of cavity enhanced DOAS (CE-DOAS) to perform sensitive and selective point measurements of multiple trace gases with a single instrument. In contrast to other broad-band CEAS techniques, CE-DOAS relies only on the measurement of relative intensity changes, i.e., does not require knowledge of the light intensity in the absence of trace gases and aerosols (I0) and is therefore insensitive to lamp drifts and/or the presence of aerosols. We have built a prototype LED-CE-DOAS instrument in the blue spectral range (420-490nm) to measure nitrogen dioxide (NO2), glyoxal (CHOCHO), methylglyoxal (CH3COCHO), iodine monoxide (IO), water (H2O) and oxygen dimers (O4). Aerosol extinction is retrieved at two wavelengths by means of observing water and O4 and measuring pressure, temperature and relative humidity independently. The instrument components are presented, and the approach to measure aerosol extinction is demonstrated by means of a set of experiments where laboratory generated monodisperse aerosols are added to the cavity. The aerosol extinction cross section agrees well with Mie calculations, demonstrating that our setup enables measurements of the above gases in open cavity mode.
TUESDAY, February 2, 2010
Environmental Analysis of Water and Food Samples by Advanced Mass Spectrometry Techniques
Imma Ferrer and E. Michael Thurman
Environmental, Civil, and Architectural Engineering
The analysis of pharmaceuticals and pesticides in water and food is one of the hot topics in environmental analysis. Recently the Associated Press published an article that much of the drinking water of the US is affected by pharmaceuticals coming from our wastewater. This article was backed up by numerous scientific studies since the late 1990s showing pharmaceuticals occurring in surface waters of the US. We have established a Laboratory for Environmental Mass Spectrometry soon to be a Center for Environmental Mass Spectrometry that uses an array of state of the art MS, including LC/time-of-flight MS, triple quadrupole MS with Jetspray, LC/MS ion trap, and other instrumentation to examine questions such as pharmaceuticals in drinking water and pesticides in food. Our seminar will discuss our new Center of Environmental MS, instrumentation, and applications to pharmaceuticals in drinking water and pesticides in food.
FRIDAY, January 22, 2010 (note special day)
University of British Columbia, Canada
CIRES Auditorium @ 4:00 p.m University of Colorado, Boulder
Trapping organic aerosol ions for molecular identification: Some lessons learned
The incapability of off-line techniques to resolve a significant part of the organic fraction of atmospheric aerosols has resulted in a stronger focus in recent years on developing real time aerosol mass spectrometers that are able to identify not just compound classes, but specific molecules. The approach chosen in most cases has been reducing fragmentation by use of soft-ionization techniques. While use of soft ionization can greatly simplify the mass spectra of complex mixtures, it also tends to erase the chemical information provided by the fragmentation pattern. Therefore, the ability to isolate and obtain tandem MS spectra of individual molecular ions is key to be able to id individual compounds.
Ion traps are compact, versatile devices that are similarly well suited for use in single particle mass spectrometers (SP-MS) than the more ubiquitous reflectron time-of-flight-MS; however, unlike reTOFs, they can also be used for tandem MS experiments. We have recently build a single particle ion trap mass spectrometer (SPIT-MS) that combines in-trap IR laser desorption of particles with a state-of-the-art laser based tabletop tunable VUV source. This allows separate optimization of both the desorption and ionization step for minimal fragmentation and -at high enough IR fluencies- a quantitative response. At the same time, measurements of the first ionization energy of the molecular ion together with their tandem MS spectrum can be used for molecular identification.While the SPIT-MS works as intended with certain types of test aerosol, it mostly fails with mixtures of aliphatic compounds, its intended target. The reasons for this failure will be examined in detail and some of its implications for alternative designs discussed.
In the second part of the talk, two other simpler SPIT-MS designs recently developed at UBC will be discussed:
- A laboratory prototype that uses pulsed IR laser desorption and conventional pulsed 70 eV electron impact for ionization. While its overall performance is comparable to the Aerodyne TOF in single particle mode, in addition it allows for analysis of refractory material as well as tandem MS analysis of larger ions.
- A new field capable ITMS that combines a novel aerosol beam alignment design with a mass spectrometer with dual polarity detection. Ionization occurs by laser ablation at 266 nm. This instrument is currently being deployed to the top of Whistler Mountain, BC to study long range transport of Asian dust.
MONDAY, November 30, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
Synthesis of Catalyst Arrays from Nanoparticle Precursors
The desire to develop novel, more efficient heterogeneous catalysts is a vital area of research in renewable energy applications. Due to the huge compositional and structural parameter space under which solid state materials can exist, it is nearly impossible to develop new heterogeneous catalysts a-priori. Therefore, many research groups have turned to combinatorial methods to identify new materials. While methods of synthesizing combinatorial arrays of bulk materials are well established, combinatorial arrays of nano-materials have been more elusive. Here we present a novel synthesis methodology for arrays of nanoparticles on solid supports using nanoparticles as synthetic precursors. The combinatorial arrays are generated by utilizing multidirectional nanoparticle gradients created by exploiting the kinetics of electrostatic adhesion of nanoparticles to a solid support. Subsequent reaction of the solid supports at elevated temperatures causes adjacent particles to alloy yielding nanoparticles with a gradient of compositions. These reactions have been demonstrated to take place on solid supports in both gaseous and liquid environments. Nanoparticle arrays adsorbed onto indium tin oxide (ITO) coated glass have been shown to alloy in a similar fashion. The arrays on ITO glass were subsequently fabricated into working electrodes for an electrochemical cell. The electrodes were then demonstrated as a catalyst screening tool for methanol fuel cell catalysts.
MONDAY, November 2, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
A Novel Method for Analysis of Respirable Particle Size Distributions using an Andersen Cascade Impactor
Andersen cascade impactors (ACIs) are widely used throughout the pharmaceutical industry to obtain aerodynamic particle size distributions for inhalable products. An ACI separates aerosolized particles by passing them through a series of orifice‐containing stages and plates; the plate on which a certain particle will deposit depends on its velocity and aerodynamic diameter. A limitation encountered with the use of this instrument is that the analytical method chosen to quantify the deposition of particles on each plate must be precise, accurate, and have a low detection limit. A method that measures the total organic carbon (TOC) content on each plate has been found to fulfill many of the requirements needed to obtain accurate particle size distributions.
Amperometric S-Nitrosothiol Sensors: Applications and Methods
It has been discovered that the right amount of S-nitrosothiol (RSNO) species in blood prevents the activation of clotting agents. A new RSNO detection technique, based on an electrochemical sensor, rapidly measures the level of RSNOs in whole blood. Use of this S-nitrosothiol sensor during surgical procedures, like Extra Corporeal Life Support (ECLS), could provide physicians with a novel method of monitoring a patient’s health. This seminar is an opportunity to describe the methods of the S-nitrosothiol biosensor’s assembly and in vivo testing.
MONDAY, October 26, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
Practical Analytical Chemistry - Colorimetric Wet Chemistry Methods for Wastewater, Drinking Water, and Natural Water
Analytical chemistry is an essential tool in drinking water and wastewater regulation. Wet Chemistry specifically refers to analytical chemistry performed in aqueous solution. It is therefore easily performed in the same matrix as wastewater and drinking water. This presentation will cover three wastewater testing methods: EPA 420.1, which tests for all phenols/phenolic compounds; EPA 365.3 dissolved, which tests for the orthophosphate ion in a filtered solution; and SM 3500-Cr B, which tests for hexavalent chromium in natural or treated water. Each of these tests is colorimetric, and the chemistry of their respective color-producing reaction will be discussed, as well as typical matrix interferences.
MONDAY, October 19, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
Sources of organic aerosols: atmospheric transformations of emissions from combustion systems
Carnegie Mellon University
Atmospheric particles play an important role in climate forcing; they are also strongly associated with adverse human health effects. Organic aerosols account for a large fraction of ambient fine particle mass, but their sources and transformation processes are still poorly understood. Motor vehicles, wood stoves, and other combustion systems are major sources of organic aerosols. This talk discusses recent field, laboratory, and modeling results on organic particle emissions from combustion systems. The results reveal a dynamic picture in which low-volatility organics evaporate, oxidize, and recondense as they are transported away from the source. This new picture alters our understanding of the contribution of combustion sources to urban and regional pollution and brings chemical transport model predictions into better agreement with field observations. The talk concludes with a discussion of the implications of these recent findings on human exposures and the design of regulations to control organic aerosols.
MONDAY, October 12, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
New Insights Into the Mechanism of 3-Hydroxy-3-Methylglutaryl Coenzyme A Reductase
Class II 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, the rate limiting enzyme of the mevalonate pathway, represents an attractive potential target for the development of antibiotics the against multiple drug-resistant strains of Gram-positive cocci. However, recent steady-state spectrofluorimetric studies suggest that the mechanism of catalysis does not go through a mevaldehyde intermediate as accepted in the literature. The objective of this study was to investigate HMG-CoA reductase catalysis prior to steady-state conditions to determine if this incongruence was the result of a fast equilibrium. Stopped-flow kinetic assays, with dead times of 8 ms, were conducted to probe for the elusive mevaldehyde intermediate. Results found that a fast equilibrium can not account for the absence of mevaldehyde, suggesting a revision of the current literature-accepted mechanism of catalysis to one where coenzyme A plays a more integral role.
A NEGATIVE ION PHOTOELECTRON SPECTROSCOPIC STUDY OF Mo2-.
The homonuclear diatomic metal ion Mo2- was studied using negative ion photoelectron spectroscopy. This bare, homonuclear group 6 transition metal dimer allows the study of multiple metal-metal bonding free of ligand effects. The photoelectron spectra, obtained at 488 nm with an instrumental resolution of about 6 meV (50 cm-1), provide measurements of the electron affinities, vibrational frequencies for both the anion and the neutral states, and bond length changes upon electron detachment. The Mo2- spectra displays a transition to the multiply-bonded 1Σg+(dπ)4(dδ)4(dσ)2(sσ)2 ground state of the neutral molecule. In the anion, the extra electron occupies the vacant antibonding sσ* orbital, giving a 2Σu+ ground state.
MONDAY, October 5, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
Aerosols of the Past: Lessons from Saturn’s Moon Titan
Dept. Chem & Biochem., and CIRES, CU-Boulder
An organic haze layer in the upper atmosphere of Titan plays a crucial role in the atmospheric composition and climate of that moon. Photochemistry in the atmosphere of the early Earth shortly after the time of planetary formation may have led to a similar haze. However, due to differences in atmospheric chemistry, the aerosols formed on the early Earth may have had distinct chemical and optical properties from those suspected to make up the hazes on Titan. We have conducted laboratory experiments simulating photochemical haze production on Titan and early Earth. The resulting aerosols are analyzed using an Aerosol Mass Spectrometer (AMS) to obtain compositional information and extinction cavity ring down (CRD) spectroscopy to determine the optical properties of the particles. The hazes on the two worlds will be compared and the implications of haze on the climate and habitability of ancient Earth will be discussed.
What have we learned about organic aerosol sources and processing? What’s next?
Dept. Chem & Biochem., and CIRES, CU-Boulder
Aerosols play major roles in climate forcing and the hydrological cycle, and also on human health effects, visibility degradation, and deposition of acids, toxics, and nutrients to ecosystems. Organic aerosols (OA) account for a large fraction (~50%) of ambient submicron aerosol mass, but their sources and transformation processes are still poorly understood. I will summarize recent findings about the sources, processing and budget of OA arising from multiple field and lab studies, as well as comparisons to 1D and 3D models. OA from all sources evolves in the atmosphere by becoming more oxygenated and hygroscopic and less volatile, and partially losing the chemical signature of the original source and gaining a common signature of atmospheric oxidation. Secondary OA (SOA) formation in urban areas is greatly underestimated by traditional models, in contrast with biogenic SOA formed under pristine conditions which is reasonably predicted. New models close the gap and even exceed the observed SOA in urban areas, but it is not clear whether this is for the right reasons. Further progress necessitates more complete high-quality measurements at one location as well as new measurement & analysis techniques, and we are preparing for two such campaigns in Los Angeles, CA in 2010 and Manitou Springs, CO in 2011.
MONDAY, September 28, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
Water and photon mediated chemistry relevant to atmospheric aerosol formation
Dept. Chem & Biochem., and CIRES, CU-Boulder
Research in the Vaida group explores the interface between physical chemistry and atmospheric science using tools of spectroscopy, photochemistry and photoreaction dynamics. This presentation will exemplify discuss water catalyzed photochemical reactions of oxidized organic species (acids, alcohols, aldehydes and ketones) relevant to atmospheric chemistry. Our approach utilizes electronic and vibrational spectroscopy to explore chemical reactions. Theoretical modeling in collaboration with the skodje group elucidates the roles of cluster conformation and dynamical effects in the photochemical processes. The specific example of methyl glyoxal, and pyruvic and glyoxilic acids and of their hydrates will be presented. The discussion will point to the role of water and photon mediated chemistry of organic molecules to the generation and processing of secondary organic aerosols and, more generally, to climate.
Instrument development for use in field and laboratory experiments in the ATMOSpeclab
Dept. Chem & Biochem., and CIRES, CU-Boulder
The Atmospheric Trace Molecule Spectroscopy Laboratory (ATMOSpeclab) was established in 2007 at CU Boulder to develop and apply optical spectroscopic instruments to measure atmospheric composition of reactive trace gases in polluted urban, and pristine natural atmospheric environments. Specific atmospheric chemistry projects in the ATMOSpeclab will be discussed, and include: - Impact of halogen chemistry on Mercury deposition in the coastal environment - Airborne MAX-DOAS from research aircraft - Ship based MAX-DOAS in the Southern Hemisphere Pacific Ocean - Laboratory studies of SOA formation from glyoxal in simulation chambers - Development of a detailed model to represent SOA formation via the aerosol aqueous phase
MONDAY, September 21, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
CU Inhalable Dry Powder Vaccines have Provided Protection Against Infection
R. Sievers, S. Cape, J. Burger, D. McAdams, J. Manion, L. Rebits, S. Winston, B. Quinn, J. Searles, D. Krank, P. Bhagwat, P. Pathak, A. Genosar, R. Dhere, V. Vaidya, R. Muley, D. Griffin, W-H Lin, and P. Rota
Protection against infection with measles virus has been demonstrated in animal models immunized 14 months earlier by inhalation of CU-invented dry powder vaccine microparticles. Needle-free aerosol delivery of dry powder vaccines may provide an effective and low-cost means of immunization. Powder manufacturing with gentle, rapid drying by Carbon Dioxide Assisted Nebulization with a Bubble Dryer (CAN-BD) appears to be an attractive alternative to freeze drying of sensitive biologicals like live attenuated Edmonston-Zagreb measles virus vaccine. Stability of measles virus in glassy, dry, respirable microparticles made by CAN-BD with less than 1% water sealed in unidose aluminum foil has been demonstrated. The dry powder aggregate, upon dispersion from an active dry powder inhaler, deposits in the moist respiratory tract where the microparticles rapidly dissolve within minutes. Antibiotics are also being studied and delivered as microparticles against infectious diseases.
Funded by FNIH Grant 1077.
Improving the Performance of Li Ion Batteries Using Atomic Layer Deposition
Steven M. George
Depts. of Chemistry and Chemical Engineering University of Colorado, Boulder, CO 80309 Steven.George@Colorado.Edu
Lithium ion batteries (LIBs) are emerging as the dominant power source for portable electronics. Improvement in their capacity lifetime during charge-discharge cycles must be achieved before LIBs can be used for plug-in-hybrid and electric vehicles. LiCoO2 and graphite are common cathode and anode materials, respectively, for LIBs. The capacity loss of LIBs is linked to electrode deterioration caused by interfacial reactions with the electrolyte, dissolution of the metal oxide cathodes and structural instabilities caused by volume expansion during lithium intercalation. Atomic layer deposition (ALD) is based on the strategy of sequential, self-limiting surface reactions to deposit inorganic materials. ALD can deposit thin, conformal films on cathode and anode materials in LIBs to provide chemical protection, restrict dissolution and stabilize structural changes. Our recent work has demonstrated that ultrathin Al2O3 ALD films can improve the capacity stability of LiCoO2 cathodes and graphite anodes. Additional work is developing new protective coatings that will serve as an artificial solid-electrolyte interphase (SEI) for further stability improvement.
MONDAY, September 14, 2009
4:00 p.m. CIRES Auditorium University of Colorado, Boulder
Renewable and Sustainable Energy Institute (RASEI): What does this mean for the Dept. of Chemistry and Biochemistry (and other departments and institutes)?
Carl A. Koval, Co-Director
In June 2009, the University of Colorado’s Board of Regents approved the formation of a new campus institute: RASEI (pronounced ‘racy”). This formation of this institute grew out of the former CU-Boulder Energy Initiative (EI), which was created in early 2006. In addition, administrators at CU-Boulder and the National Renewable Energy Laboratory (NREL) in Golden signed a MOU to operate RASEI as a joint institute. In this presentation, I will focus on:
• the transition of the EI to RASEI, from initiative to institute;
• opportunities for faculty to be involved in RASEI governance and programs;
• opportunities for students to be involved RASEI’s research, teaching, commercialization and outreach activities.
For more information about RASEI, go to http://rasei.colorado.edu.
Research at the Interface of Nanoscale Materials and Biology
Daniel L. Feldheim
Dept. Chem & Biochem., CU-Boulder
Between the size scale of individual biomacromolecules and cellular organelles lies a size regime―the few nm to 100 nm range―that is not readily probed using existing technologies. Thus, while a vast inventory of RNA and protein sequences and structures are being catalogued, a quantitative cellular context for these structures is lagging. Yet to understand this context would be to know how collections of individual macromolecules assemble into the dynamic machines that form a living cell. Once these interactions are revealed, a new picture of the cell and its disease states is sure to emerge.
With achievable 2 nm resolution and perfect preservation of cellular structure, electron tomography (ET) now represents the highest resolution technique for examining biomolecules in their native cellular context. Indeed, cell biologists now dream of generating 3D images containing the entire proteome of a living cell. This dream remains out of reach, not because ET cannot visualize individual proteins, but because it is simply not possible currently to know which protein is which in a tomographic cellular reconstruction.
This presentation will describe methods being developed in our lab for creating electron dense nanoparticle tags for identifying cellular biomolecules by ET. These methods rely on the discovery of materials ribozymes and enzymes―RNA and protein/peptide sequences that can catalyze the formation of inorganic nanoparticles and control nanoparticle growth. The isolation and structure-function relationships of a number of materials ribozymes and enzymes will be shown.
In addition to visualizing biomolecule interactions in cells, we are working on ways to mimic and disrupt such interactions for disease treatment. We view this largely as a materials problem as well, and have been learning how to design metal nanoclusters to effectively interact with cellular biomolecules. A few lessons learned in our studies of cell and nuclear targeting and the prevention of viral infection will be described.
THURSDAY, September 10, 2009
4:00 p.m. CIRES Auditorium (note change of location) University of Colorado, Boulder
What controls the diurnal variability of carbon dioxide and reactive species? (a.k.a. "Boundary Layers for Chemists")
Jordi Vilà-Guerau de Arellano
Meteorology and Air Quality Section
Wageningen University (The Netherlands)
We examine the main physical and chemical processes that determine the diurnal variability of atmospheric compounds in the boundary layer. In addition to surface processes, turbulent mixing and reactivity, we put special emphasis on investigating the role of the exchange of heat, water and chemical species between the free troposphere and the atmospheric boundary layer, namely the entrainment process. This process enhances the dilution of compounds and introduces free tropospheric air masses with different characteristics into the atmospheric boundary layer.
In the seminar, I will discuss several cases where entrainment plays a major role in the evolution of atmospheric compounds. By analyzing observational evidence or performing numerical experiments by the large eddy simulation technique and a conceptual (mixed-layer theory) model, we are able to find the contribution of entrainment to the diurnal variability of carbon dioxide or isoprene. Particular emphasis is placed on the need to maintain a balance in dynamic processes and the specific characteristic of each atmospheric compound.