On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol
Item
Title (Dublin Core)
On the effectiveness of nitrogen oxide reductions as a control over ammonium nitrate aerosol
Description (Dublin Core)
Nitrogen oxides (NO<sub><i>x</i></sub>) have fallen steadily across the US over the last 15 years. At the same time, NO<sub><i>x</i></sub> concentrations decrease on weekends relative to weekdays, largely without co-occurring changes in other gas-phase emissions, due to patterns of diesel truck activities. These trends taken together provide two independent constraints on the role of NO<sub><i>x</i></sub> in the nonlinear chemistry of atmospheric oxidation. In this context, we interpret interannual trends in wintertime ammonium nitrate (NH<sub>4</sub>NO<sub>3</sub>) in the San Joaquin Valley of California, a location with the worst aerosol pollution in the US and where a large portion of aerosol mass is NH<sub>4</sub>NO<sub>3</sub>. Here, we show that NO<sub><i>x</i></sub> reductions have simultaneously decreased nighttime and increased daytime NH<sub>4</sub>NO<sub>3</sub> production over the last decade. We find a substantial decrease in NH<sub>4</sub>NO<sub>3</sub> since 2000 and conclude that this decrease is due to reduced nitrate radical-initiated production at night in residual layers that are decoupled from fresh emissions at the surface. Further reductions in NO<sub><i>x</i></sub> are imminent in California, and nationwide, and we make a quantitative prediction of the response of NH<sub>4</sub>NO<sub>3</sub>. We show that the combination of rapid chemical production and efficient NH<sub>4</sub>NO<sub>3</sub> loss via deposition of gas-phase nitric acid implies that high aerosol days in cities in the San Joaquin Valley air basin are responsive to local changes in NO<sub><i>x</i></sub> within those individual cities. Our calculations indicate that large decreases in NO<sub><i>x</i></sub> in the future will not only lower wintertime NH<sub>4</sub>NO<sub>3</sub> concentrations but also cause a transition in the dominant NH<sub>4</sub>NO<sub>3</sub> source from nighttime to daytime chemistry.
Creator (Dublin Core)
Pusede, S. E.
Duffey, K. C.
Shusterman, A. A.
Saleh, A.
Laughner, J. L.
Wooldridge, P. J.
Zhang, Q.
Parworth, C. L.
Kim, H.
Capps, S. L.
Valin, L. C.
Cappa, C. D.
Fried, A.
Walega, J.
Nowak, J. B.
Weinheimer, A. J.
Hoff, R. M.
Berkoff, T. A.
Beyersdorf, A. J.
Olson, J.
Crawford, J. H.
Cohen, R. C.
Date (Dublin Core)
2018-09-08
Type (Dublin Core)
Text
Format (Dublin Core)
application/pdf
Identifier (Dublin Core)
10.5194/acp-16-2575-2016
https://acp.copernicus.org/articles/16/2575/2016/
Source (Dublin Core)
eISSN: 1680-7324
Language (Dublin Core)
eng
