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Published December 10, 2021 | Published + Supplemental Material
Journal Article Open

Ozone chemistry in western U.S. wildfire plumes

Abstract

Wildfires are a substantial but poorly quantified source of tropospheric ozone (O₃). Here, to investigate the highly variable O₃ chemistry in wildfire plumes, we exploit the in situ chemical characterization of western wildfires during the FIREX-AQ flight campaign and show that O₃ production can be predicted as a function of experimentally constrained OH exposure, volatile organic compound (VOC) reactivity, and the fate of peroxy radicals. The O₃ chemistry exhibits rapid transition in chemical regimes. Within a few daylight hours, the O₃ formation substantially slows and is largely limited by the abundance of nitrogen oxides (NOₓ). This finding supports previous observations that O₃ formation is enhanced when VOC-rich wildfire smoke mixes into NOₓ-rich urban plumes, thereby deteriorating urban air quality. Last, we relate O₃ chemistry to the underlying fire characteristics, enabling a more accurate representation of wildfire chemistry in atmospheric models that are used to study air quality and predict climate.

Additional Information

© 2021 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC). Received: 8 July 2021. Accepted: 20 October 2021. We thank P. P. Papin for providing the background picture in Fig. 1 and R. Schwantes and M. Bela for helpful discussions. A.W. acknowledges support from ASAP-FFG-BMVIT and thanks T. Mikoviny and L. Tomsche for field support. L.X., K.T.V., H.A., J.D.C., and P.O.W. acknowledge NASA grants 80NSSC18K0660 and 80NSSC21K1704. I.B., M.M.C., G.I.G., A.L., J.A.N., J.P., P.S.R., M.A.R., and C.C.W. acknowledge the NOAA Cooperative Agreement with CIRES, NA17OAR4320101. G.M.W., T.F.H., J.M.S., J. Liao, and R.A.H. acknowledge NASA Tropospheric Composition and NOAA AC4 grant NA17OAR4310004. R.J.Y. and V.S. acknowledge NOAA grant NA16OAR4310100. A.F., D.R., J.W., and P.W. acknowledge NASA grant 80NSSC18K0628. D.A.P. acknowledges NASA grant 80HQTR18T0063. S.R.H. and K.U. acknowledge NASA grant 80NSSC18K0638. A.J.S. and E.M.G. acknowledge NASA grant 80NSSC18K0685. H.G., P.C.-J., and J.L.J. acknowledge NASA grants 80NSSC18K0630 and 80NSSC19K0124. F.P. acknowledges support from the EU (#674911, IMPACT ITN). C.D.H. acknowledges NASA grant 80NSSC18K0625. Author contributions: L.X. and P.O.W. designed the research. J.H.C., C.W., and D.A.P. designed the flight plans. L.X., J.D.C., K.T.V., H.A., P.O.W., I.B., S.S.B., P.C.-J., M.M.C., J.P.D., G.S.D., A.F., J.B.G., G.I.G., H.G., J.W.H., S.R.H, H.A.H., T.F.H., R.A.H., C.D.H., L.G.H., E.M.G., J.L.J., A.L.,Y.R.L., J. Liao, J. Lindaas, J.A.N., J.B.N., J.P., F.P., D.R., P.S.R., M.A.R., A.W.R., T.B.R., K.S., V.S., T.S., A.J.S., J.M.S., D.J.T., K.U., P.R.V., J.W., C.W., R.A.W., P.W., A.W., G.M.W., and C.C.W. conducted measurements. L.X. analyzed the data. L.X., P.O.W., and J.D.C. wrote the paper. R.J.Y. provided critical context on fire chemistry. The authors declare that they have no competing interests. Data and materials availability: All data needed to evaluate the conclusions in the paper are present in the paper and/or the Supplementary Materials. FIREX-AQ data are available at www-air.larc.nasa.gov/cgi-bin/ArcView/firexaq.

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Additional details

Created:
August 22, 2023
Modified:
October 23, 2023