Spatio-Temporal Study of Methylmercury Biogeochemistry in Wetlands of the Southern Lake Michigan Watershed

摘要

Mercury pollution in aquatic ecosystems occurs from a combination of atmospheric deposition, a process that tends to deposit Hg relatively evenly across a region the size of the Grand Calumet watershed, and legacy contamination, which can be distributed very unevenly due to geological processes or to point discharges. In addition, the variability in biological and geochemical factors between particular aquatic ecosystems can lead to their having very different levels of methylmercury (MeHg) in the water even with comparable rates of Hg inputs from deposition and legacy contamination. Since MeHg is the only form of Hg that biomagnifies in food webs, MeHg levels in biota can also exhibit a high degree of spatial variability. Consequently, predicting what ecosystems within a landscape will have the greatest problems is challenging for environmental managers, who are simultaneously seeking to maximize the human use of natural resources and protect humans and wildlife. The goal of this project has been to apply state-of-the-art methods in Hg analysis in support of this management objective.