Nitrogen oxides undergo several heterogeneous reactions that are important to the oxidizing capacity of the atmosphere on local, regional and global scales. Uptake of N2O5 has a highly variable rate and proceeds either via hydrolysis to HNO3 or reaction with aerosol chloride to yield ClNO2. The former is one of the most important sinks for NOx, with subsequent influence for regional and global O3 and OH budgets. The latter leads to NOx transport and a source of chlorine radicals through photolysis. Heterogeneous conversion of NO2 to HONO has long been recognized as an important local and regional source of OH radicals via HONO photolysis, but rates and mechanisms for the heterogeneous process, especially if it is driven photochemically, remain uncertain and controversial. Heterogeneous reactions are often difficult to incorporate into atmospheric models because of the challenges in accurately predicting the available aerosol or ground surface area, as well as the dependence of heterogeneous reaction rates on aerosol composition and relative humidity. Ambient measurements of nitrogen species can provide constraints on the rates and products of their heterogeneous reactions, as well as offer mechanistic insight into the underlying chemistry. This presentation will survey results from recent field studies, including aircraft campaigns, that serve to better define these important atmospheric chemical processes.

Heterogeneous chemistry of nitrogen oxides: Results from recent field studies

249th National Meeting (2015)

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