Linking Cellulose Fiber Sediment Methyl Mercury Levels to Organic Matter Decay and Major Element Composition
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Methylation of mercury (Hg) to highly toxic methyl Hg (MeHg), a process known to occur when organic matter (OM) decomposition leads to anoxia, is considered a worldwide threat to aquatic ecosystems and human health. We measured temporal and spatial variations in sediment MeHg, total Hg (THg), and major elements in a freshwater lagoon in Sweden polluted with Hg-laden cellulose fibers. Fiber decomposition, confined to a narrow surface layer, resulted in loss of carbon (C), uptake of nitrogen (N), phosphorus (P), and sulfur (S), and increased MeHg levels. Notably, fiber decomposition and subsequent erosion of fiber residues will cause buried contaminants to gradually come closer to the sediment–water interface. At an adjacent site where decomposed fiber accumulated, there was a gain in C and a loss of S when MeHg increased. As evidenced by correlation patterns and vertical chemical profiles, reduced S may have fueled C-fixation and Hg methylation at this site.
KeywordsMercury Methylation Cellulose fiber Decomposition Major element cycles
This study was part of a project initiated and run by the Kalmar County Administration and financed by the Swedish EPA. We thank the project manager Anna Aleljung and also Tommy Hammar, Kalmar County Administration and Bo Troedsson, Eman Catchment Management Association for taking part in the planning of the project and for providing equipment for field measurement and field sampling. As always, the mercury laboratory at IVL, Gothenburg determined mercury and methyl mercury with high accuracy and precision.
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