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Atmospheric Chemistry and Physics










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 southeastern US during the NOMADSS 2013 summer field study. The daytime HONO concentration ranged from low parts per trillion by volume (pptv) in the free troposphere (FT) to mostly within 5–15 pptv in the background planetary boundary layer (PBL). There was no discernible vertical HONO gradient above the lower flight altitude of 300 m in the PBL, and the transport of ground surface HONO was not found to be a significant contributor to the tropospheric HONO budget. The total in situ HONO source mean (±1 SD) was calculated as 53 (±21) pptv h−1 during the day. The upper-limit contribution from NOx-related reactions was 10 (±5) pptv h−1, and the contribution from photolysis of particulate nitrate (pNO3) was 38 (±23) pptv h−1, based on the measured pNO3 concentrations and the median pNO3 photolysis rate constant of 2.0 × 10−4 s−1 determined in the laboratory using ambient aerosol samples. The photolysis of HONO contributed to less than 10 % of the primary OH source. However, a recycling NOx source via pNO3photolysis was equivalent to ∼ 2.3 × 10−6 mol m−2 h−1 in the air column within the PBL, a considerable supplementary NOx source in the low-NOx background area. Up to several tens of parts per trillion by volume of HONO were observed in power plant and urban plumes during the day, mostly produced in situ from precursors including NOx and pNO3. Finally, there was no observable accumulation of HONO in the nocturnal residual layer and the nocturnal FT in the background southeastern US, with an increase in the HONO ∕ NOx ratio of ≤ 3 × 10−4 h−1 after sunset.


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, Thomas Karl10,Julie Haggerty7, Samuel Hall7, Kirk Ullmann7,James Smith7,11, and John Ortega7

1State Key Joint Laboratory of Environmental Simulation and Pollution Control, College of Environmental Sciences and Engineering, Peking University, Beijing, China
2Wadsworth Center, New York State Department of Health, Albany, NY
3Department of Environmental Health Sciences, State University of New York, Albany, NY
4Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA
5Department of Atmospheric and Oceanic Sciences, University of Colorado-Boulder, Boulder, Colorado
6Department of Physics, University of Helsinki, Helsinki, Finland
7National Center for Atmospheric Research, Boulder, Colorado
8Department of Earth System Science, University of California, Irvine, CA
9Institute for Environmental and Climate Research, Jinan University, Guangzhou, China
10Institute of Atmospheric and Cryospheric Sciences, University of Innsbruck, Innsbruck, Austria
11University of Eastern Finland, Kuopio, Finland

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This work is licensed under a Creative Commons Attribution 4.0 License.