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Active and widespread halogen chemistry in the tropical and subtropical free troposphere

Wang, Siyuan, Schmidt, Johan A., Baidar, Sunil, Coburn, Sean, Dix, Barbara, Koenig, Theodore K., Apel, Eric, Bowdalo, Dene, Campos, Teresa L., Eloranta, Ed, Evans, Mathew J., DiGangi, Joshua P., Zondlo, Mark A., Gao, Ru-Shan, Haggerty, Julie A., Hall, Samuel R., Hornbrook, Rebecca S., Jacob, Daniel, Morley, Bruce, Pierce, Bradley, Reeves, Mike, Romashkin, Pavel, ter Schure, Arnout, Volkamer, Rainer
Proceedings of the National Academy of Sciences of the United States of America 2015 v.112 no.30 pp. 9281-9286
air, altitude, bioaccumulation, bromine, climate models, developing countries, emissions, energy, fish, mercury, neurotoxins, ozone, public health, storms, troposphere, Nevada, Southeastern United States
Our measurements show that tropospheric halogen chemistry has a larger capacity to destroy O ₃ and oxidize atmospheric mercury than previously recognized. Halogen chemistry is currently missing in most global and climate models, and is effective at removing O ₃ at altitudes where intercontinental O ₃ transport occurs. It further helps explain the low O ₃ levels in preindustrial times. Public health concerns arise from bioaccumulation of the neurotoxin mercury in fish. Our results emphasize that bromine chemistry in the free troposphere oxidizes mercury at a faster rate, and makes water-soluble mercury available for scavenging by thunderstorms. Naturally occurring bromine in air aloft illustrates global interconnectedness between energy choices affecting mercury emissions in developing nations and mercury deposition in, e.g., Nevada, or the southeastern United States.