Scientists at IQFR publish in Nature Communications a new atmospheric Hg photoreduction process that changes how this contaminant is transported and deposited over terrestrial ecosystems.

Anthropogenic mercury emissions are primarily in the gaseous elemental form. In the atmosphere, mercury emissions oxidize to gaseous Hg(II) compounds that are more soluble and deposited to eh surface by rain. Atmospheric reduction of Hg(II) competes with deposition, thereby modifying the magnitude and pattern of Hg deposition. In this study, we bring together novel theoretical, experimental and modelling methods to identify the photoreduction of oxidized mercury as the main reduction pathway for atmospheric mercury which substantially changes global Hg dynamics. The inclusion of this new photochemical scheme in global atmospheric models leads to an important increase in atmospheric Hg lifetime. Likewise, 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.   

Alfonso Saiz-Lopez, Sebastian P. Sitkiewicz, Daniel Roca-Sanjuán, Josep M. Oliva-Enrich, Juan Z. Dávalos, Rafael Notario, Martin Jiskra, Yang Xu, Feiyue Wang, Colin P. Thackray, Elsie M. Sunderland, Daniel J. Jacob, Oleg Travnikov, Carlos A. Cuevas, A. Ulises Acuña, Daniel Rivero, John M.C. Plane, Douglas E. Kinnison & Jeroen E. Sonke. Photoreduction of gaseous oxidized mercury changes global atmospheric mercury speciation, transport and depositionNature Communications.  DOI: 10.1038/s41467-018-07075-3, 2018.

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