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Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
https://doi.org/10.5194/acp-2018-105
© Author(s) 2018. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
13 Feb 2018
Review status
This discussion paper is a preprint. It is a manuscript under review for the journal Atmospheric Chemistry and Physics (ACP).
Tropospheric HONO Distribution and Chemistry in the Southeast U.S.
Chunxiang Ye1,2, Xianliang Zhou2,3, Dennis Pu3, Jochen Stutz4, James Festa4, Max Spolaor4, Catalina Tsai4, Christopher Cantrell5, Roy L. Mauldin III5,6, Andrew Weinheimer7, Rebecca S. Hornbrook7, Eric C. Apel7, Alex Guenther8, Lisa Kaser7, Bin Yuan9,10, Thomas Karl11, Julie Haggerty7, Samuel Hall7, Kirk Ullmann7, James Smith7,12, and John Ortega7 1College of Environmental Sciences and Engineering, Peking University, Beijing, 100871, China
2Wadsworth Center, New York State Department of Health, Albany, NY, USA
3Department of Environmental Health Sciences, State University of New York, Albany, NY, USA
4Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA
5Department of Atmospheric and Oceanic Sciences, University of Colorado-Boulder, Boulder Colorado, USA
6Department of Physics, University of Helsinki, Helsinki, Finland
7National Center for Atmospheric Research, Boulder, Colorado, USA
8Department of Earth System Science, University of California, Irvine, CA, USA
9NOAA, Earth System Research Laboratory, Chemical Sciences Division, Boulder, Colorado, USA
10Cooperative Institute for Research in Environmental Sciences, University of Colorado at Boulder, Boulder, CO, USA
11Institute of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria
12University of Eastern Finland, Kuopio, Finland
Abstract. Here we report the measurement results of nitrous acid (HONO) and a suite of relevant parameters on the NCAR C-130 research aircraft in the Southeast U.S. during NOMADSS 2013 summer field study. Daytime HONO concentrations ranged from low parts per trillion by volume (pptv) in the free troposphere (FT) to mostly within 5–15 pptv in the background terrestrial air masses, and to up to 40 pptv in the industrial and urban plumes in the planetary boundary layer (PBL). There was no discernable vertical HONO distribution trend in the PBL above the lowest flight altitude of 300 m, indicating that the ground surface HONO source was not a significant contributor to the HONO budget in the measurement altitude between 300 m and 4.7 km. While there was a strong correlation between the concentrations of HONO and oxides of nitrogen (NOx = NO + NO2) (R2 = 0.52), the sum of all known NOx-related HONO formation mechanisms was found to account for less 20 % of the daytime HONO source in the background terrestrial air masses, due to the low level of NOx and surface area density of aerosol particles. Photolysis of particulate nitrate (pNO3) appeared to be the major daytime HONO source in the background terrestrial air masses, based on the measured pNO3 concentration and the median value of 2.0 × 10−4 s−1 for pNO3 photolysis rate constant determined in the laboratory using ambient aerosol samples collected during the field study. Within the power plant and industrial plumes encountered, daytime HONO was predominantly produced by secondary formation processes involving both NOx and pNO3 as precursors. While HONO was not a significant OH precursor compared to O3 under low NOx conditions in the air column, it was an important intermediate product of a photochemical renoxification process recycling nitric acid and nitrate back to NOx. Finally, the HONO / NOx ratio stayed relatively constant for several hours after sunset in the nocturnal residual layer, suggesting no significant night-time volume HONO source existed in the nocturnal residual layer and the nocturnal FT under background conditions.

Citation: Ye, C., Zhou, X., Pu, D., Stutz, J., Festa, J., Spolaor, M., Tsai, C., Cantrell, C., Mauldin III, R. L., Weinheimer, A., Hornbrook, R. S., Apel, E. C., Guenther, A., Kaser, L., Yuan, B., Karl, T., Haggerty, J., Hall, S., Ullmann, K., Smith, J., and Ortega, J.: Tropospheric HONO Distribution and Chemistry in the Southeast U.S., Atmos. Chem. Phys. Discuss., https://doi.org/10.5194/acp-2018-105, in review, 2018.
Chunxiang Ye et al.
Chunxiang Ye et al.
Chunxiang Ye et al.

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Short summary
Substantial levels of HONO existed during the day throughout the troposphere over the Southeast U.S. during NOMADSS 2013 summer field study. Particulate nitrate photolysis appeared to be the major volume HONO source, while NOx was an important HONO precursor only in industrial and urban plumes. HONO was not a significant OH radical precursor in the rural troposphere away from the ground surface; however, its production from particulate nitrate photolysis was an important renoxification pathway.
Substantial levels of HONO existed during the day throughout the troposphere over the Southeast...
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