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

AbstractAnthropogenic 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.

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Details

Published: Nov 15, 2018
Vol/Issue: 9(1)
License: View

Authors

A

Alfonso Saiz-Lopez

Atmospheric Chemistry and Climate Group, Institute of Physical Chemistry Rocasolano, CSIC , 28006 Madrid, Spain

S

Sebastian P. Sitkiewicz

Kimika Fakultatea, Euskal Herriko Unibertsitatea UPV/EHU and Donostia International Physics Center (DIPC), P.K. 1072, 20080 Donostia, Euskadi, Spain

D

Daniel Roca-Sanjuán

Institut de Ciència Molecular, Universitat de València, Valencia 46071, Spain

J

Josep M. Oliva-Enrich

J

Juan Z. Dávalos

Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid 28006, Spain

Harvard John A. Paulson School of Engineering and Applied Sciences, Harvard University, Cambridge Massachusetts 02138, United States

Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid 28006, Spain

A

A. Ulises Acuña

Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid 28006, Spain

D

Daniel Rivero

Department of Atmospheric Chemistry and Climate, Institute of Physical Chemistry Rocasolano, CSIC, Madrid 28006, Spain

Cite This Article

Alfonso Saiz-Lopez, Sebastian P. Sitkiewicz, Daniel Roca-Sanjuán, et al. (2018). Photoreduction of gaseous oxidized mercury changes global atmospheric mercury speciation, transport and deposition. Nature Communications, 9(1). https://doi.org/10.1038/s41467-018-07075-3

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

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