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A winning proposal for the Innovative Research Program, 2008: Emissions of Acidic Trace Gases from Forest FiresInvestigators: Joost de Gouw and Carsten Warneke (CIRES), and Jim Roberts (NOAA) Theme: Regional Processes Objective(s): We propose the use of a newly developed chemical ionization mass spectrometer (CIMS) for measurements of acidic trace gases from burning vegetation at the Fire Sciences Laboratory in Missoula, Montana. The goal is to quantify the atmospheric source of organic and inorganic trace gases from forest fires, which are suspected to be a large fraction of the total emissions, and to assess their potential to contribute to aerosol formation. Background and importance: Forest fires are one of the important issues at the nexus of air quality and climate change. The frequency and intensity of wildfires is widely expected to increase due to global change with far reaching consequences for air quality, the global carbon cycle and climate change. For example, emissions from wildfires in the western U.S. have the potential to impact air quality at large distances from the sources [1]. Also, a significant fraction of atmospheric aerosol has been shown to originate from biomass burning [2] with important ramifications to the direct and indirect effects of aerosol on climate. There are still many unknowns about the emissions of trace gases and aerosol from forest fires. Part of this is caused by the unpredictability of fires, which hinders systematic field studies. Much has been learned from burning in the laboratory, for example at the Fire Sciences Laboratory operated by the U.S. Forest Service in Missoula, Montana [3]. From these studies it is clear that a large fraction of the gaseous emissions consists of oxygenated organic species, acids in particular: an observation that has been confirmed by field measurements [4]. Acidic trace gases are among the hardest trace gases to measure, however, and as a result there is only good data for the 2 simplest organic acids (formic and acetic acid). We have recently developed a novel CIMS method to measure acidic trace gases based on the use of acetate ions, CH3C(O)O-, which readily react with most organic and many inorganic acids by proton transfer [5]. Here we propose to take the CIMS instrument to the Fire Sciences Laboratory and to measure the acidic trace gases emitted from burning vegetation collected in different areas of the country (California, Arizona, North Carolina and Florida). The results of this work are important for 2 different reasons. First, a large fraction of organic trace gases in the atmosphere consists of acids [6] and the emissions are therefore important to understand in the description of the organic carbon budget, which is currently under intense investigation and discussion [6,7]. Second, di-carboxylic acids are an important component of secondary organic aerosol (SOA), which formation mechanism is poorly understood [8]. What makes this innovative? Existing methods for organic acids are time consuming, prone to measurement artifacts and only provide long-term averages, and are therefore hardly suitable to follow the rapidly changing concentrations in a transient fire experiment. The method we propose to use has (i) a fast time response (1 sec) to evaluate the Acid/CO and Acid/CO2 ratios in real time, (ii) a high sensitivity (20 pptv) to measure even the smallest emissions and (iii) can be used for a much wider range of species than previously observed. Expected outcome and impact: This work will potentially provide the first emission factors for a wide range of organic and inorganic acids from forest fire emissions. These emission factors are important inputs to analyses and models that assess the regional to global effects of biomass burning. In addition, the emission ratios from this work will be highly useful for the interpretation of field data, for example as we hope to obtain from the CalNex study in California in 2010 that is currently being planned by NOAA. Research plan: The research will be conducted along the following lines:
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216 UCB