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Atmospheric Chemistry and Physics









The lifetime of nitrogen oxides (NOx) affects the concentration and distribution of NOx and the spatial patterns of nitrogen deposition. Despite its importance, the lifetime of NOx is poorly constrained in rural and remote continental regions. We use measurements from a site in central Alabama during the Southern Oxidant and Aerosol Study (SOAS) in summer 2013 to provide new insights into the chemistry of NOx and NOx reservoirs. We find that the lifetime of NOx during the daytime is controlled primarily by the production and loss of alkyl and multifunctional nitrates (ΣANs). During SOAS, ΣAN production was rapid, averaging 90 ppt h−1 during the day, and occurred predominantly during isoprene oxidation. Analysis of the ΣAN and HNO3 budgets indicate that ΣANs have an average lifetime of under 2 h, and that approximately 45 % of the ΣANs produced at this site are rapidly hydrolyzed to produce nitric acid. We find that ΣAN hydrolysis is the largest source of HNO3 and the primary pathway to permanent removal of NOx from the boundary layer in this location. Using these new constraints on the fate of ΣANs, we find that the NOx lifetime is 11 ± 5 h under typical midday conditions. The lifetime is extended by storage of NOx in temporary reservoirs, including acyl peroxy nitrates and ΣANs.


Paul S. Romer1, Kaitlin C. Duffey1, Paul J. Wooldridge1, Hannah M. Allen2,3, Benjamin R. Ayres2, Steven S. Brown4, William H. Brune5, John D. Crounse6, Joost de Gouw4,7, Danielle C. Draper2,8, Philip A. Feiner5, Juliane L. Fry2, Allen H. Goldstein9,10, Abigail Koss4,7, Pawel K. Misztal10, Tran B. Nguyen6,11, Kevin Olson10, Alex P. Teng6, Paul O. Wennberg6,12, Robert J. Wild4,7, Li Zhang5, and Ronald C. Cohen1,13

1Department of Chemistry, University of California at Berkeley, Berkeley, CA, USA
2Department of Chemistry, Reed College, Portland, OR, USA
3Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA, USA
4Chemical Sciences Division, Earth System Research Laboratory, National Oceanic and Atmospheric Administration, Boulder, CO, USA
5Department of Meteorology, Pennsylvania State University, University Park, PA, USA
6Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA, USA
7Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder, CO, USA
8Department of Chemistry, University of California, Irvine, CA, USA
9Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, CA, USA
10Department of Environmental Science, Policy and Management, University of California at Berkeley, Berkeley, CA, USA
11Department of Environmental Toxicology, University of California, Davis, CA, USA
12Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, USA
13Department of Earth and Planetary Sciences, University of California at Berkeley, Berkeley, CA, USA