The Science of the total environment
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Wetlands have been identified as important sites of mercury methylation in catchments, but the range of wetland types and their geographic distribution for which methylmercury fluxes are reported in the literature are limited. Linkages among wetland hydrology, total mercury and methylmercury concentrations and fluxes, and other water quality parameters were assessed in a temperate forested swamp in Southern Ontario, Canada. Two hydrogeomorphically distinct stream reaches within the wetland exhibited differences in wetland-stream hydrologic connectivity, which strongly influenced mercury dynamics. ⋯ Both total mercury and methylmercury concentrations were related to dissolved and particulate organic carbon in stream waters, but these relationships were dependent upon the sampling location and flow conditions. Throughout the wetland, methylmercury concentrations exhibited temporal relationships with sulfate concentrations. Further, despite short surface water residence times, periods of wetland and stream disconnect and high pH (approx. 8) in surface water, methylmercury fluxes from this wetland to the downstream were similar to those from more stagnant and acidic wetlands.
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Sci. Total Environ. · Jun 2004
Influence of methylmercury from tributary streams on mercury levels in Savannah River Asiatic clams.
Average methylmercury levels in five Savannah River tributary streams, sampled 11 times over 2 years (0.170 ng/l), were nearly twice as high as in the Savannah River (0.085 ng/l). Total mercury levels in the tributaries (2.98 ng/l) did not differ significantly from the river (2.59 ng/l). ⋯ Mercury concentrations in Asiatic clams (Corbicula fluminea) collected from the discharge plumes of Savannah River tributaries (average of 0.044 microg/g wet weight) were significantly (P<0.001) higher than in Asiatic clams collected from the Savannah River upstream from the tributary mouths (average of 0.017 microg/g wet weight). These results indicate that streams draining wetlands into coastal plain rivers can create localized areas of elevated methylmercury with resulting increases in the mercury levels of river biota.
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Sci. Total Environ. · Mar 2004
Coregionalization analysis of heavy metals in the surface soil of Inner Mongolia.
Due to potential problems associated with their deficiencies or toxicities, heavy metals in soils are of great environmental concern. To evaluate heavy metal contents and their relationships in the surface soil of Inner Mongolia, soil samples were collected from 344 sites and contents of copper, lead, zinc, cadmium, nickel, chromium, mercury, cobalt, vanadium and manganese were determined. In this article, coregionalization of these ten heavy metals is investigated using factorial kriging. ⋯ At the scale of 200 km, heavy metal relationships mainly reflect the result of biocycling. Their relationships at the intermediate scale (400 km) are thought to be derived from the atomic substitution of metals in the parent materials. Effects of soil pH on the adsorption of heavy metals by soil organic materials could explain their relationships at the large spatial scale (over 1000 km).
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Total mercury (THg) concentrations in streams draining cultivated watersheds in Minnesota, USA are strongly correlated with total suspended sediment (TSS) concentrations, varying widely in response to precipitation-driven inputs of soil-derived suspended sediments. Methylmercury (MeHg) concentrations in these waterways have not been studied, and little is known about mercury uptake mechanisms in resident fish populations. To begin to identify factors influencing MeHg concentrations and loadings in these streams, we measured THg and MeHg concentrations in unfiltered whole water samples from the Minnesota River and two of its major tributaries, the Blue Earth and Le Sueur Rivers. ⋯ A late-October increase in MeHg concentration attributed to leaf litter inputs was also observed in this river. MeHg concentration trends in the Minnesota River were similar to those in the Blue Earth River. Indicators of biological productivity (chlorophyll a, volatile suspended solids, and total Kjeldahl nitrogen) were higher in the Blue Earth and Minnesota Rivers compared to the Le Sueur River, which may signal a connection between higher biological activity and increased MeHg concentrations.
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Sci. Total Environ. · Sep 1999
Marine radioactivity in the Arctic: a retrospect of environmental studies in Greenland waters with emphasis on transport of 90Sr and 137Cs with the East Greenland Current.
The waters around Greenland have received radioactive contamination from three major sources: Global fallout, discharges from the nuclear fuel reprocessing plant Sellafield in the UK, and the Chernobyl accident in the Former Soviet Union (FSU). The global fallout peaked in the early 1960s. The radiologically most important radionuclides from this source are 90Sr and 137Cs. ⋯ Dumping of nuclear waste in the Kara and Barents Seas may be another, although minor source. From measurements in Greenland waters carried out since 1962 the transport of radionuclides with the East Greenland Current is calculated and compared with the estimated inputs of 90Sr and 137Cs to the Arctic Ocean. This study focus on 90Sr and 137Cs because the longest time series are available for these two radionuclides.