Cooperative Institute for Research in Environmental Sciences

Science Rendezvous > 2009 Posters
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Sensitive, in-situ detection of nitrogen oxides, NO_2 , NO_3 and N_2 O_5 ; Design, performance and instrument validation

Hendrik Fuchs, William P. Dubé and Steven S. Brown

Nitrogen oxides (NO_x = NO + NO_2 ) play a key role in the chemistry of the troposphere, serving as catalysts for the photochemical production of ozone in summer and leading to the formation of nitrate aerosol in winter. At night they are largely converted via reaction with ozone to the higher oxides, the nitrate radical (NO_3 ) and dintrogen pentoxide (N_2 O_5 ). Recent advances in optical technology have allowed for /in-situ/ detection of these nocturnal nitrogen oxides, whose chemistry is important to lifetimes and budgets of NO_x , O_3 and VOC. NO_3 is readily detected on its visible absorption bands near 660 nm via pulsed cavity ring-down spectroscopy, a high-sensitivity, direct absorption method capable of sub-pptv detection limits with an integration time of 1 s. N_2 O_5 is detected via. the same method subsequent to its thermal conversion to NO_3 , and NO_2 is detected by visible cavity ring-down spectroscopy at 532 nm in the same instrument. The instrument has been deployed during several recent NOAA field campaigns on ships, aircraft, a tall tower, and at ground sites. It has also recently participated in a validation campaign at a large environmental simulation chamber (SAPHIR) in Jülich, Germany. The presentation will give an overview of the instrument operation and performance as well as its comparison to other measurements.