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Organic Material:  The Primary Control on Mercury Methylation and Ambient Methyl Mercury Concentrations in Estuarine Sediments:  
Umeå University, Faculty of Science and Technology, Chemistry. Umeå University, Faculty of Science and Technology, Umeå Marine Sciences Centre (UMF).
2006 (English)In: Environmental Science & Technology, Vol. 40, no 6, 1822-9 p.Article in journal (Refereed) Published
Abstract [en]

Estuarine environments that have no direct sources of mercury (Hg) pollution may have sediment concentrations of methylmercury (MeHg) as high as those of polluted marine environments. In this study we examined the biogeochemical factors affecting net methylation and sediment MeHg concentrations in an unpolluted estuarine environment, the Öre River estuary, which discharges into the Bothnian Bay (20-120 ng total Hg g-1 dry sediment, salinity 3-5‰). We analyzed the spatial and temporal differences in surface sediment profiles of MeHg concentration, Hg methylation, MeHg demethylation, and concentrations of sulfide and oxygen between accumulation and erosion type bottoms. The main difference between the bottoms studied was in the proportion of organic material (OM) in the sediment, ranging between 0.8% and 10.8%. The pore water sulfide concentration profiles also differed considerably between sites and seasons, from 0 to 20 μM, with 100 μM as the extreme maximum. The sediment MeHg concentration profiles (0-10 cm) mostly varied between 0.1 and 7 ng g-1 dry weight (dw, as Hg). The MeHg demethylation rates were relatively low and the depth profiles of the rates were relatively constant over season, site, and depth. In contrast, both rates and depths of maximum Hg methylation differed between the bottoms. The results indicate that the amount of OM accumulated at the bottoms was the main factor affecting net MeHg production, while the total amount of Hg had little or no influence on the amount of MeHg in the sediment.

Place, publisher, year, edition, pages
ACS Publications , 2006. Vol. 40, no 6, 1822-9 p.
URN: urn:nbn:se:umu:diva-22984DOI: 10.1021/es051785hOAI: diva2:218912
Available from: 2009-05-25 Created: 2009-05-25 Last updated: 2009-05-25Bibliographically approved
In thesis
1. Mercury species transformations in marine and biological systems studied by isotope dilution mass spectrometry and stable isotope tracers
Open this publication in new window or tab >>Mercury species transformations in marine and biological systems studied by isotope dilution mass spectrometry and stable isotope tracers
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the implementation of species-specific isotope dilution (SSID) methodology and stable isotope tracers to determine mercury species occurrence and transformation processes in-situ and during sample treatment. Isotope enriched tracers of methyl-, ethyl- and inorganic mercury were synthesised and applied in different combinations to marine and biological samples. Experimental results were obtained using gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS).

Mercury methylation and methylmercury demethylation processes in surface sediments were studied in the brackish Öre River estuary, Bothnian Bay. Uni- and multivariate data evaluation identified the organic material content and mercury methylation potential in the sediments as important factors controlling incipient methylmercury levels. Mercury species distribution in mice treated with the pharmaceutical preservative Thimerosal (ethylmercurithiosalicylate) was studied. The ethylmercury moiety of Thimerosal was observed to rapidly convert to inorganic mercury in the mice during the treatment period as well as during sample treatment, hence necessitating SSID methodology for accurate ethylmercury determinations in biological samples.

To facilitate the introduction of SSID as a routine quantitative method in mercury speciation, a methylmercury isotopic certified reference material (ICRM) was produced. Prior to certification, the stability of the material was examined in conventional and isochronous stability studies spanning 12 months, which permitted uncertainty estimation of the methylmercury amount content for two years of shelf-life.

Finally, a field-adapted SSID method for methylmercury determinations in natural water samples was developed. The proposed analytical protocol significantly simplified sample storage- and treatment procedures without sacrifices in analytical accuracy.

Place, publisher, year, edition, pages
Umeå: Kemi, 2005. 38 p.
Analytical chemistry, Mercury, methylmercury, ethylmercury, Thimerosal, speciation, methylation, demethylation, brackish water sediment, natural waters, GC-ICP-MS, species-specific isotope dilution, isotope enriched tracers, Analytisk kemi
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
urn:nbn:se:umu:diva-467 (URN)91-7305-838-6 (ISBN)
Public defence
2005-04-01, KB3A9, Kemiskt Biologiskt Centrum (KBC), Umeå Universitet 90187, Umeå, 10:00 (English)
Available from: 2005-03-09 Created: 2005-03-09 Last updated: 2009-05-25Bibliographically approved

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