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Mercury Methylation Rates for Geochemically Relevant HgII Species in Sediments.
MedLine Citation:
PMID:  23017152     Owner:  NLM     Status:  Publisher    
Monomethylmercury (MeHg) in fish from freshwater, estuarine and marine environments are a major global environmental issue. Mercury levels in biota are mainly controlled by the methylation of inorganic mercuric mercury (HgII) to MeHg in water, sediments and soils. There is, however, a knowledge gap concerning the mechanisms and rates of methylation of specific geochemical HgII species. Such information is crucial for a better understanding of variations in MeHg concentrations among ecosystems and, in particular, for predicting the outcome of currently proposed measures to mitigate mercury emissions and reduce MeHg concentrations in fish. To fill this knowledge gap we propose an experimental approach using HgII isotope tracers, with defined and geochemically important adsorbed and solid HgII forms in sediments, to study MeHg formation. We report HgII methylation rate constants, km, in estuarine sediments which span over two orders of magnitude depending on chemical form of added tracer: metacinnabar (β-201HgS(s)) < cinnabar (α-199HgS(s)) < HgII reacted with mackinawite (≡FeS-202HgII) < HgII bonded to natural organic matter (NOM-196HgII) < a typical aqueous tracer (198Hg(NO3)2(aq)). We conclude that a combination of thermodynamic and kinetic effects of HgII solid-phase dissolution and surface desorption control the HgII methylation rate in sediments and causes the large observed differences in km-values. The selection of relevant solid-phase and surface adsorbed HgII tracers will therefore be crucial to achieving biogeochemically accurate estimates of ambient HgII methylation rates.
Sofi Jonsson; Ulf Skyllberg; Mats B Nilsson; Per-Olof Westlund; Andrey Shchukarev; Erik Lundberg; Erik Björn
Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-9-28
Journal Detail:
Title:  Environmental science & technology     Volume:  -     ISSN:  1520-5851     ISO Abbreviation:  Environ. Sci. Technol.     Publication Date:  2012 Sep 
Date Detail:
Created Date:  2012-9-28     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  0213155     Medline TA:  Environ Sci Technol     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
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