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Isotopic Evidence for Determining the Sources of Dissolved Organic Sulfur in a Forested Catchment
- Kang, Phil-Goo, Mitchell, Myron J., Mayer, Bernhard, Campbell, John L.
- Environmental Science & Technology 2014 v.48 no.19 pp. 11259-11267
- acidification, aluminum, biogeochemistry, forested watersheds, groundwater, methylmercury compounds, solutes, stable isotopes, streams, sulfur, surface water, toxicity, Adirondacks, New York
- Understanding sulfur (S) biogeochemistry, especially in those watersheds subject to elevated levels of atmospheric S inputs, is needed for determining the factors that contribute to acidification, nutrient losses and the mobilization of toxic solutes (e.g., monomeric aluminum and methylmercury). S is found in a variety of both organic and inorganic forms undergoing a range of biotic and abiotic transformations. In watersheds with decreasing atmospheric S inputs, internal cycling is becoming dominant in affecting whether there is net loss or retention of S. Little attention has been given to the role of dissolved organic S (DOS) in affecting S biogeochemistry. DOS originates from assimilatory and bacterial dissimilatory S reduction (BDSR), the latter of which produces ³⁴S-depleted S. Within groundwater of the Archer Creek Catchment in the Adirondack Mountains (New York) there was reoxidation of reduced S, which was an important source of SO₄²–. DOS in surface waters had a higher variation of δ³⁴S–DOS values (−6.0 to +8.4‰) than inorganic S with δ³⁴S–SO₄²– values ranging from +1.0 to +5.8‰. Inverse correlations between δ³⁴S values of SO₄²– and DOS suggested that BDSR played an important role in producing DOS.