Isotopic evidence for determining the sources of dissolved organic sulfur in a forested catchment

Abstract

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 SO₄^2-. DOS in surface waters had a higher variation of δ³⁴S-DOS values (-6.0 to +8.4‰) than inorganic S with δ³⁴S-SO₄^2- values ranging from +1.0 to +5.8‰. Inverse correlations between δ³⁴S values of SO₄^2- and DOS suggested that BDSR played an important role in producing DOS.

Citation

Kang, Phil-Goo; Mitchell, Myron J.; Mayer, Bernhard; Campbell, John L. 2014. Isotopic evidence for determining the sources of dissolved organic sulfur in a forested catchment. Environmental Science & Technology. 48(19): 11259-11267.