Journal
SCIENCE OF THE TOTAL ENVIRONMENT
Volume 452, Issue -, Pages 196-207Publisher
ELSEVIER
DOI: 10.1016/j.scitotenv.2013.02.052
Keywords
Mercury; Environmental archives; Sediments; Mercury deposition models; Peat; Ice
Categories
Funding
- Northern Contaminants Program (Canada)
- Geological Survey of Canada
- AMAP
- MIKA/DANCEA
- AU BSS Arctic Research Initiative, AU Herning
- Norden Top-level Research Initiative sub-program 'Effect Studies and Adaptation to Climate Change' through the Nordic Centre of Excellence for Strategic Adaptation Research (NORD-STAR)
- Danish Environmental Protection Agency
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This review compares the reconstruction of atmospheric Hg deposition rates and historical trends over recent decades in the Arctic, inferred from Hg profiles in natural archives such as lake and marine sediments, peat bogs and glacial firn (permanent snowpack), against those predicted by three state-of-the-art atmospheric models based on global Hg emission inventories from 1990 onwards. Model veracity was first tested against atmospheric Hg measurements. Most of the natural archive and atmospheric data came from the Canadian Greenland sectors of the Arctic, whereas spatial coverage was poor in other regions. In general, for the Canadian Greenland Arctic, models provided good agreement with atmospheric gaseous elemental Hg (GEM) concentrations and trends measured instrumentally. However, there are few instrumented deposition data with which to test the model estimates of Hg deposition, and these data suggest models over-estimated deposition fluxes under Arctic conditions. Reconstructed GEM data from glacial firn on Greenland Summit showed the best agreement with the known decline in global Hg emissions after about 1980, and were corroborated by archived aerosol filter data from Resolute, Nunavut The relatively stable or slowly declining firn and model GEM trends after 1990 were also corroborated by real-time instrument measurements at Alert, Nunavut, after 1995. However, Hg fluxes and trends in northern Canadian lake sediments and a southern Greenland peat bog did not exhibit good agreement with model predictions of atmospheric deposition since 1990, the Greenland firn GEM record, direct GEM measurements, or trends in global emissions since 1980. Various explanations are proposed to account for these discrepancies between atmosphere and archives, including problems with the accuracy of archive chronologies, climate-driven changes in Hg transfer rates from air to catchments, waters and subsequently into sediments, and post-depositional diagenesis in peat bogs. However, no general consensus in the scientific community has been achieved. (C) 2013 Elsevier B.V. All rights reserved.
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