| Popis: |
A geochemical model for sulfur in soft water lake sediments of the Adirondack Mountains, New York, is developed to gain insight into the timing and magnitude of historical changes in sulfur loading. Surficial sulfur concentrations range from 3500 to 10,000 {mu}g g{minus}{sup 1}, increase to 6000 to >20,000 {mu}g g{minus}{sup 1} at a depth of 2-6 cm, and then decrease downcore to background levels of 2500-7500 {mu}g g{minus}{sup 1}. Sulfate concentrations are about 50-80 {mu}M in the overlying water and decrease rapidly below the sediment-water interface. A mathematical model is constructed assuming sulfur is incorporated into sediments by burial of detrital organic matter and by diffusion of dissolved sulfate from the overlying water with subsequent fixation into the sediment solids. Several scenarios of historical sulfate deposition were examined as model boundary conditions. The observed sediment sulfur profiles are best modeled using boundary conditions showing loading increases of about a factor of 8 since about 1940. Assuming as much as a decade of retention of sulfate within the terrestrial portion of the ecosystem, this suggests that significant increases in sulfate deposition rates began sometime about 1930 in this area. 34 refs., 7 figs., 2 tabs. |
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