Photoreduction of gaseous oxidized mercury changes global atmospheric mercury speciation, transport and deposition

Saiz-Lopez, Alfonso and Sitkiewicz, Sebastian P. and Roca-Sanjuán, Daniel and Oliva-Enrich, Josep M. and Dávalos, Juan Z. and Notario, Rafael and Jiskra, Martin and Xu, Yang and Wang, Feiyue and Thackray, Colin P. and Sunderland, Elsie M. and Jacob, Daniel J. and Travnikov, Oleg and Cuevas, Carlos A. and Acuña, A. Ulises and Rivero, Daniel and Plane, John M. C. and Kinnison, Douglas E. and Sonke, Jeroen E.. (2018) Photoreduction of gaseous oxidized mercury changes global atmospheric mercury speciation, transport and deposition. Nature communications, 9 (1). p. 4796.

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Anthropogenic mercury (Hg(0)) emissions oxidize to gaseous Hg(II) compounds, before deposition to Earth surface ecosystems. Atmospheric reduction of Hg(II) competes with deposition, thereby modifying the magnitude and pattern of Hg deposition. Global Hg models have postulated that Hg(II) reduction in the atmosphere occurs through aqueous-phase photoreduction that may take place in clouds. Here we report that experimental rainfall Hg(II) photoreduction rates are much slower than modelled rates. We compute absorption cross sections of Hg(II) compounds and show that fast gas-phase Hg(II) photolysis can dominate atmospheric mercury reduction and lead to a substantial increase in the modelled, global atmospheric Hg lifetime by a factor two. Models with Hg(II) photolysis show enhanced Hg(0) deposition to land, which may prolong recovery of aquatic ecosystems long after Hg emissions are lowered, due to the longer residence time of Hg in soils compared with the ocean. Fast Hg(II) photolysis substantially changes atmospheric Hg dynamics and requires further assessment at regional and local scales.
Faculties and Departments:05 Faculty of Science > Departement Umweltwissenschaften
UniBasel Contributors:Jiskra, Martin
Item Type:Article, refereed
Article Subtype:Research Article
Note:Publication type according to Uni Basel Research Database: Journal article
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Last Modified:12 Feb 2019 16:44
Deposited On:12 Feb 2019 16:44

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