Collaborative Research: NO3 induced nighttime air chemistry

Affiliation(s)PIProject periodFunded by
DAS Goliff, Wendy S 07/01/2007 - 06/30/2011 National Science Foundation

Project Description

The research objective is to evaluate the role of nitrate radical (NO3) and its effects on the transformation and removal of atmospheric compounds. This research will provide the first continuous measurements of nitrate radical over a multi-day period in an arid urban location over the United States. The nitrate radical plays an important role in the nighttime chemistry of the troposphere. Formed through the reaction of NO2 with O3, nitrate reacts rapidly to oxidize aldehydes and alkenes, and converts reactive nitrogen oxides to unreactive nitric acid. Averaged over 24 hours, NO3 may be as important as daytime HO for direct oxidation of alkenes and aldehydes, and particularly the ?leaf alcohols? (alcohols which also contain double bonds). The formation of NO3 can be an indirect sink of reactive nitrogen oxides if it reacts with NO2 to form dinitrogen pentoxide (N2O5). If liquid water coated surfaces are present than the N2O5 will be converted to nitric acid and thus reduce N2O5 and consequently NO3 mixing ratios. Measurements made under arid conditions allow NO3 mixing ratios to be observed under conditions of lower relative humidity then possible elsewhere. Arid conditions are a new chemical regime for NO3 because its conversion to N2O5, which in turn reacts with liquid water, placing a significant limit on its lifetime. The resulting dataset will be useful for determining the relative importance of NO3 sinks under a much wider set of conditions then is now available