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Published November 29, 2016 | Supplemental Material + Published
Journal Article Open

Persistent sulfate formation from London Fog to Chinese haze

Abstract

Sulfate aerosols exert profound impacts on human and ecosystem health, weather, and climate, but their formation mechanism remains uncertain. Atmospheric models consistently underpredict sulfate levels under diverse environmental conditions. From atmospheric measurements in two Chinese megacities and complementary laboratory experiments, we show that the aqueous oxidation of SO_2 by NO_2 is key to efficient sulfate formation but is only feasible under two atmospheric conditions: on fine aerosols with high relative humidity and NH_3 neutralization or under cloud conditions. Under polluted environments, this SO_2 oxidation process leads to large sulfate production rates and promotes formation of nitrate and organic matter on aqueous particles, exacerbating severe haze development. Effective haze mitigation is achievable by intervening in the sulfate formation process with enforced NH_3 and NO_2 control measures. In addition to explaining the polluted episodes currently occurring in China and during the 1952 London Fog, this sulfate production mechanism is widespread, and our results suggest a way to tackle this growing problem in China and much of the developing world.

Additional Information

© 2016 National Academy of Sciences. Freely available online through the PNAS open access option. Contributed by Mario J. Molina, October 9, 2016 (sent for review July 8, 2016; reviewed by Zhanqing Li and Sasha Madronich). Published ahead of print November 14, 2016. G.W. acknowledges the National Natural Science Foundation of China and the Strategic Priority Research Program of the CAS for financial support (Grants 41325014, XDA05100103, and XDB05020401). This work was partially supported by the Robert A. Welch Foundation (Grant A-1417), the Ministry of Science and Technology of China (Grant 2013CB955800), a collaborative research program by Texas A&M University and the National Natural Science Foundation of China. M.H. acknowledges the National Basic Research Program, China Ministry of Science and Technology (Grant 2013CB228503), National Natural Science Foundation of China (Grant 21190052) and the China Ministry of Environmental Protection's Special Funds for Scientific Research on Public Welfare (Grant 20130916). W.M.-O. was supported by the National Science Foundation Graduate Research Fellowship Program, and B.P. was supported by the NASA Earth and Space Science Fellowship Program. Author contributions: G.W. and R.Z. designed research; G.W., R.Z., M.E.G., L.Y., M.L.Z., M.H., Y. Lin, J.P., S.G., J.M., J.L., C.C., T.H., Y.R., Y.S.W., J.G., J.W., P.T., W.M.-O., J.S., Z.D., J.Z., Y.H., Y.W., Y.Z., Y. Li, J.H., B.P., Y.C., Y.J., F.Z., and M.J.M. performed research; G.W., R.Z., M.H., and M.J.M. contributed new reagents/analytic tools; G.W., R.Z., M.E.G., L.Y., M.L.Z., M.H., Y. Lin, J.P., J.C., Z.A., W.Z., G.L., D.S., L.Z., M.S., W.W., Y.W., L.C., D.R., P.S.L., R.A.D., C.E.K., and M.J.M. analyzed data; and G.W. and R.Z. wrote the paper. Reviewers: Z.L., University of Maryland; and S.M., National Center for Atmospheric Research. The authors declare no conflict of interest. This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1616540113/-/DCSupplemental.

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Published - PNAS-2016-Wang-13630-5.pdf

Supplemental Material - pnas.1616540113.sapp.pdf

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Additional details

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