Unexpected anthropogenic emission decreases explain recent atmospheric mercury concentration declines

Anthropogenic activities emit ~2,000 Mg y<sup>-1</sup> of the toxic pollutant mercury (Hg) into the atmosphere, leading to long-range transport and deposition to remote ecosystems. Global anthropogenic emission inventories report increases in Northern Hemispheric (NH) Hg emissions during the last three decades, in contradiction with the observed decline in atmospheric Hg concentrations at NH measurement stations. Many factors can obscure the link between anthropogenic emissions and atmospheric Hg concentrations, including trends in the reemissions of previously released anthropogenic ("legacy") Hg, atmospheric sink variability, and spatial heterogeneity of monitoring data. Here, we assess the observed trends in gaseous elemental mercury (Hg<sup>0</sup>) in the NH and apply biogeochemical box modeling and chemical transport modeling to understand the trend drivers. Using linear mixed effects modeling of observational data from 51 stations, we find negative Hg<sup>0</sup> trends in most NH regions, with an overall trend for 2005 to 2020 of -0.011 ± 0.006 ng m<sup>-3</sup> y<sup>-1</sup> (±2 SD). In contrast to existing emission inventories, our modeling analysis suggests that annual NH anthropogenic emissions must have declined by at least 140 Mg between the years 2005 and 2020 to be consistent with observed trends. Faster declines in 95th percentile Hg<sup>0</sup> values than median values in Europe, North America, and East Asian measurement stations corroborate that the likely cause is a decline in nearby anthropogenic emissions rather than background legacy reemissions. Our results are relevant for evaluating the effectiveness of the Minamata Convention on Mercury, demonstrating that existing emission inventories are incompatible with the observed Hg<sup>0</sup> declines.

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Publication Details

Journal
Proceedings of the National Academy of Sciences
Published
2024-10-08
DOI
https://doi.org/10.1073/pnas.2401950121
Citations
17
Primary Topic
Mercury impact and mitigation studies
Type
article
Field-Weighted Citation Impact
5.35

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article

Unexpected anthropogenic emission decreases explain recent atmospheric mercury concentration declines

Ðanilo Custódio, Winston T. Luke, Marijana Murovec, Koketso M. Molepo et al.
17 citations
Proceedings of the National Academy of Sciences
Mercury impact and mitigation studies
5.35
article

Unexpected anthropogenic emission decreases explain recent atmospheric mercury concentration declines

Ðanilo Custódio, Winston T. Luke, Marijana Murovec, Koketso M. Molepo, Christine F. Braban, Julian Rüdiger, Vincent L. St. Louis, Sarah R. Leeson, Noelle E. Selin, Guey‐Rong Sheu, Daniel A. Jaffe, Michelle G. Nerentorp Mastromonaco, Matthew S. Landis, Katriina Kyllönen, Aryeh I. Feinberg, Kai‐Lan Chang, Katrine Aspmo Pfaffhuber
article en
17 citations

Abstract

Anthropogenic activities emit ~2,000 Mg y<sup>-1</sup> of the toxic pollutant mercury (Hg) into the atmosphere, leading to long-range transport and deposition to remote ecosystems. Global anthropogenic emission inventories report increases in Northern Hemispheric (NH) Hg emissions during the last three decades, in contradiction with the observed decline in atmospheric Hg concentrations at NH measurement stations. Many factors can obscure the link between anthropogenic emissions and atmospheric Hg concentrations, including trends in the reemissions of previously released anthropogenic ("legacy") Hg, atmospheric sink variability, and spatial heterogeneity of monitoring data. Here, we assess the observed trends in gaseous elemental mercury (Hg<sup>0</sup>) in the NH and apply biogeochemical box modeling and chemical transport modeling to understand the trend drivers. Using linear mixed effects modeling of observational data from 51 stations, we find negative Hg<sup>0</sup> trends in most NH regions, with an overall trend for 2005 to 2020 of -0.011 ± 0.006 ng m<sup>-3</sup> y<sup>-1</sup> (±2 SD). In contrast to existing emission inventories, our modeling analysis suggests that annual NH anthropogenic emissions must have declined by at least 140 Mg between the years 2005 and 2020 to be consistent with observed trends. Faster declines in 95th percentile Hg<sup>0</sup> values than median values in Europe, North America, and East Asian measurement stations corroborate that the likely cause is a decline in nearby anthropogenic emissions rather than background legacy reemissions. Our results are relevant for evaluating the effectiveness of the Minamata Convention on Mercury, demonstrating that existing emission inventories are incompatible with the observed Hg<sup>0</sup> declines.

Proceedings of the National Academy of SciencesVol. 121(42)
Finnish Meteorological Institute (FI), Environmental Protection Agency (US), National Oceanic and Atmospheric Administration (US), Research Triangle Park Foundation (US), University of Alberta (CA), Cooperative Institute for Research in Environmental Sciences (US), University of Colorado Boulder (US), University of Washington (US), National Central University (TW), Slovenian Environment Agency (SI), UK Centre for Ecology & Hydrology (GB), IVL Swedish Environmental Research Institute (SE), German Environment Agency (DE), University of Washington Bothell (US), Helmholtz-Zentrum Hereon (DE), Max Planck Institute for Biogeochemistry (DE), Massachusetts Institute of Technology (US), NILU (NO), NOAA Air Resources Laboratory (US)
National Science Foundation, New York State Department of Environmental Conservation, Office of Research and Development, Department for Environment, Food and Rural Affairs, UK Government, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Ministry of Environment, Environment and Climate Change Canada, Natural Environment Research Council
Life below water
Openalex Percentile: Top 4%
Mercury impact and mitigation studies
5.35
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