Spatial Patterns of Mercury in Atmospheric Deposition, Soils and Lake Biota in the Adirondack Park, New York

Mercury (Hg), as a trace element cycling in the environment, poses a serious health threat to both humans and wildlife due to its toxicity. Atmospheric deposition is the main source of Hg to most remote environments. The Adirondack Park in New York State of the United States receives moderate Hg deposition, and is a region characterized by relatively high concentrations of Hg in the terrestrial and especially aquatic biota. It is important to understand the mechanisms that contribute to the sensitivity of this region to Hg inputs. In my research, studies of the spatial patterns of Hg in atmospheric deposition, soils and lake biota were conducted as tools to characterize and quantify the inputs, transport, transformations, and bioaccumulation of Hg in the Adirondacks. Atmospheric Hg deposition was estimated using numerical modeling and limited field data. Mercury deposition to the coniferous forest, and deciduous forest during the leaf-on period was estimated as the sum of litterfall and throughfall deposition, and Hg deposition to the deciduous forest during the leaf-off period and the non-forest areas year-around was estimated as wet deposition plus modeled dry Hg deposition. Dry Hg deposition was estimated using the Big Leaf model, with consideration of elevation in the calculation of deposition velocities. Mercury and organic matter concentrations and pools in soil profiles were surveyed at 139 forest sites across the northeastern United States including the Adirondacks to study spatial patterns of soil Hg biogeochemistry. Finally Hg concentrations were characterized for the entire aquatic food chain for 44 Adirondack lakes, including lake water, littoral sediment, zooplankton, crayfish, fish and common loon. Although there were distinct spatial patterns of increasing Hg deposition with forest cover, increasing elevation, and decreasing latitude and longitude, no direct relationship were found with Hg concentrations or pools in soils or aquatic biota with atmospheric Hg deposition. The soil Hg pools were found to be related to the historical Hg deposition, while the horizonal patterns of soil Hg concentrations appear to be shaped by the depth distribution of soil organic matter. Mercury concentrations in lake biota increased with increasing position in the food chain. Methyl Hg concentrations in top predators are set by the base of the food chain and strongly increase with decrease in lake pH. My research suggests that the landscape characteristics (acidic lakes, large forest coverage) contribute to the ability of Adirondack ecosystems to process Hg inputs, convert these inputs to methyl Hg and transfer that methyl Hg to elevated concentrations in top aquatic predators