Master of Science (M.S.)
Moss Landing Marine Laboratories
Aquatic mercury (Hg) contamination and subsequent bioaccumulation pose a threat to human and ecosystem health. The mitigation of contaminated water bodies requires an understanding of natural baselines of metal concentrations and fluxes. In this study, six age-dated sediment cores were analyzed to assess temporal and spatial variability of atmospheric Hg deposition from remote natural lakes throughout California. Geochemical proxies, including 210Pb, particle size, magnetic susceptibility, organic carbon and organic nitrogen, were measured to apportion Hg concentrations between atmospheric deposition, anthropogenic and watershed processes. Anthropogenic Total Hg (HgT) lake sediment concentrations increased by factors of 2 to 10 times that of historic (pre-1850) HgT concentrations in all four lakes studied. Results support the hypothesis that atmospheric Hg deposition, and its subsequent flux to lake sediments, was the cause of elevated Hg levels and that regional sources, from both abandoned mine sites and industrial emissions, were a major source of biologically available Hg to aquatic ecosystems in California. Hence, the past biotic exposure, if scaled relative to the measured deposition, would have been 2, 5, and 10 times lower than present day levels for coastal, Central Valley, and Coastal Range aquatic systems, respectively. These values may be useful benchmarks for the development of site-specific mitigation strategies for contaminated watersheds.
Sanders, Rhea D., "A 300-year geochronological assessment of atmospheric mercury depostition in California" (2007). Capstone Projects and Theses. 81.