Deposition and Fate of Atmospheric Mercury in Forested Landscapes of the Adirondack Park, NY

In this dissertation, I investigated the deposition and fate of atmospheric mercury (Hg) to forested landscapes of the Adirondack region in Upstate New York. Despite the fact that forests are the dominant land cover in North America, there has been relatively little research on the deposition, transport, and fate of Hg within forested ecosystems. The objective of this dissertation was to quantify pathways of Hg deposition in forested sites in the Adirondack Park and to examine spatial and geographic patterns of Hg deposition and fate. The research for this dissertation was conducted in three phases. In Phase One, I compared and contrasted Hg deposition processes and Hg soil pools in a deciduous hardwood plot and a coniferous plot for 2009 and 2010 at Huntington Wildlife Forest. Mercury deposition due to litterfall was similar between the two stands, but total Hg deposition was greater in the coniferous plot due to larger fluxes of throughfall Hg. Soil evasion losses of Hg were significantly higher in the hardwood plot. Despite the fact that Hg deposition was greater and evasion losses were lower, soil Hg pools in the conifer plot were smaller than in the hardwood plot. The loss mechanism of Hg in the conifer stand is not clear. Annual variability in climate conditions was substantial between 2009 and 2010, and changes in Hg deposition quantities appear to be related to variation in temperature and precipitation quantity. In Phase Two of this dissertation, I evaluated the effects of elevation and landscape position on atmospheric Hg deposition. Two transects were established along the eastern and western sides of Whiteface Mountain in the Adirondacks. The 24 sample sites ranged from approximately 450-1450 m above sea level and covered three distinct forest types: deciduous/hardwood forest, spruce/fir conifer forest, and stunted growth alpine/fir forest. Throughfall Hg inputs and Hg accumulation in organic soils were greater in the spruce/fir and alpine areas than the deciduous forest areas. Estimates of cloud water Hg deposition demonstrate that cloud water is an important contributor to total Hg fluxes in alpine environments. Total Hg deposition was correlated to Hg concentrations in organic soil layers. Variation in both physical orographic effects and biological forest types appear to drive Hg deposition processes along this mountainous elevation gradient. In Phase Three of this study, I evaluated spatial patterns of Hg deposition by collecting canopy foliage and organic soils from 45 different plots across the Adirondack Park. The results showed species-specific differences in foliar uptake of Hg with the lowest concentrations found in first-year growth conifer needles and the highest concentrations found in black cherry (Prunus serotina). Latitude and longitude were negatively correlated with Hg concentrations in foliage and humus layer soils, while elevation was positively correlated with Hg concentrations in foliage and humus layer soils. Elemental analysis of foliage and soil also showed strong, positive correlations between Hg concentrations and nitrogen concentrations in foliage and soil. The spatial patterns of Hg deposition within the Adirondack Park are similar to patterns found for other atmospheric contaminants that originate largely from combustion sources, such as nitrogen and sulfur