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- Lambertsson, Lars, 1971-
(författare)
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Mercury species transformations in marine and biological systems studied by isotope dilution mass spectrometry and stable isotope tracers
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 2. |
- Rydberg, Johan, 1976-, et al.
(författare)
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A whole-lake basin analysis of the spatial distribution of total- and methylmercury in relation to the sediment matrix using WD-XRF and FT-IRS
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The aim of this study was to try and identify some of the factors controlling the spatial distributions of total- and methyl-Hg across a single whole-lake basin. In order to achieve this we analyzed the geochemical composition of 83 surface sediment samples from the lake Stor-Strömsjön using WD-XRF and FT-IRS. Our results show that in the north-western basin (i.e., the main recipient of the dominant inlet) total-Hg distribution is controlled by fine-grained mineral matter, while the eastern basin (which lacks major inlets) the main controlling factor is organic matter. There is only a weak correlations between methyl-Hg concentrations and either total-Hg (r2=0.12) or organic matter (r2=0.15) concentrations. Instead the distribution of methyl-Hg is largely controlled by water depth and sulfur (59 %). The spatial patterns for total-Hg concentrations vs. inventories (mass per unit area) are rather different. Even if total-Hg concentrations are about the same in locations controlled by organic matter and fine-grained mineral matter, the total-Hg inventories are much higher in the latter. For methyl-Hg the spatial distribution is patchy both for concentrations and inventories, and the highest methyl-Hg inventory was found in a shallow location with coarse-grained minerogenic sediment. The large variations in the controlling factors, even within a single whole-lake basin, suggest that lake type and surrounding catchment have an effect on the behavior of Hg. This needs to be recognized both when studying Hg loading on ecosystems, and when using lake sediments to reconstruct atmospheric Hg deposition.
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| 3. |
- Rydberg, Johan, 1976-, et al.
(författare)
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Assessing the stability of mercury and methylmercury in a varved lake sediment deposit
- 2008
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Ingår i: Environmental Science & Technology. - : American Chemical Society. - 0013-936X .- 1520-5851. ; 42:12, s. 4391-4396
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Tidskriftsartikel (refereegranskat)abstract
- Using lake sediments to infer past total mercury and methylmercury loading to the environment requires that diagenetic processes within the sediment do not significantly affect the concentrations or net accumulation rates of the mercury species. Because carbon is lost during early sediment diagenesis, the close link between carbon and mercury raises the question of how reliable lake sediments are as archives of total mercury and methylmercury loading. In this study we used a series of freeze cores taken in a lake with varved (annually laminated) sediment to assess the stability of total mercury and methylmercury over time. By tracking material deposited in specific years in cores collected in different years, we found that despite a 20–25% loss of carbon in the first 10–15 years, there was no apparent loss of total mercury over time; hence, lake sediments can be considered as reliable archives. However, over the first 5–8 years after sedimentation, about 30–40% of the methylmercury was lost (a decrease of 0.025–0.030 μg MeHg m−2 yr−1), suggesting that sediment profiles showing increasing methylmercury concentrations toward the sediment surface are in large part an artifact of diagenetic processes (net demethylation), rather than a record of changes in methylmercury loading.
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