Nitric acid and nitrate, abundant components of aerosols and the aqueous films coating urban surfaces, are thought to be a photochemical sources of nitrous acid (HONO) in the lower atmosphere during the daytime.  Unfortunately, it is not clear why HONO is formed so efficiently from these precursors, with some theories suggesting that the UV-visible absorption cross sections or quantum yields of adsorbed nitric acid or nitrate are enhanced relative to what they are in the gas phase or bulk aqueous solution.  This talk will present an overview of recent laboratory results aimed at evaluating the relative importance of pH and secondary reactions involving nitrogen dioxide to the overall yield of HONO from nitrate photolysis.  The atmospheric implications of this mechanism will be discussed, with a focus on understanding missing sources of daytime HONO.

Elucidating the mechanisms of HONO formation from nitrate photochemistry on environmental surfaces<br />

249th National Meeting (2015)

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