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An Atmospheric Constraint on the NO2 Dependence of Daytime Near-Surface Nitrous Acid (HONO)

Pusede, Sally E., VandenBoer, Trevor C., Murphy, Jennifer G., Markovic, Milos Z., Young, Cora J., Veres, Patrick R., Roberts, James M., Washenfelder, Rebecca A., Brown, Steven S., Ren, Xinrong, Tsai, Catalina, Stutz, Jochen, Brune, William H., Browne, Eleanor C., Wooldridge, Paul J., Graham, Ashley R., Weber, Robin, Goldstein, Allen H., Dusanter, Sebastien, Griffith, Stephen M., Stevens, Philip S., Lefer, Barry L., Cohen, Ronald C.
Environmental Science & Technology 2015 v.49 no.21 pp. 12774-12781
chemistry, cities, nitrogen dioxide, nitrous acid, United States
Recent observations suggest a large and unknown daytime source of nitrous acid (HONO) to the atmosphere. Multiple mechanisms have been proposed, many of which involve chemistry that reduces nitrogen dioxide (NO₂) on some time scale. To examine the NO₂ dependence of the daytime HONO source, we compare weekday and weekend measurements of NO₂ and HONO in two U.S. cities. We find that daytime HONO does not increase proportionally to increases in same-day NO₂, i.e., the local NO₂ concentration at that time and several hours earlier. We discuss various published HONO formation pathways in the context of this constraint.