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This article in JEQ

  1. Vol. 39 No. 6, p. 2200-2210
    Received: Sept 26, 2010

    * Corresponding author(s): clarksco@uwec.edu


Selenium Stable Isotope Investigation into Selenium Biogeochemical Cycling in a Lacustrine Environment: Sweitzer Lake, Colorado

  1. Scott K. Clark * and
  2. Thomas M. Johnson
  1. Dep. of Geology, Univ. of Illinois at Urbana-Champaign, 245 Natural History Building, 1301 W. Green St., Urbana, IL 61801. Scott K. Clark, current address: Geology Dep., 157 Philips Hall, Univ. of Wisconsin-Eau Claire, Eau Claire, WI 54702-4004. Assigned to Associate Editor Joselito M. Arocena


We present a comprehensive set of Se concentration and isotope ratio data collected over a 3-yr period from dissolved, sediment-hosted, and organically bound Se in a Se-contaminated lake and littoral wetland. Median isotope ratios of these various pools of Se spanned a narrow isotopic range (δ80/76SeSRM-3149 = 1.14–2.40‰). Selenium (VI) reduction in the sediments is an important process in this system, but its isotopic impact is muted by the lack of direct contact between surface waters and reduction sites within sediments. This indicates that using Se isotope data as an indicator of microbial or abiotic Se oxyanion reduction is not effective in this or other similar systems. Isotopic data suggest that most Se(IV) in the lake originates from oxidation of organically bound Se rather than directly through Se(VI) reduction. Mobilization of Se(VI) from bedrock involves only a slight isotopic shift. Temporally constant isotopic differences observed in Se(VI) from two catchment areas suggest the potential for tracing Se(VI) from different source areas. Phytoplankton isotope ratios are close to those of the water, with a small depletion in heavy isotopes (0.56‰). Fish tissues nearly match the phytoplankton, being only slightly depleted in the heavier isotopes. This suggests the potential for Se isotopes as migration indicators. Volatile, presumably methylated Se was isotopically very close to median values for phytoplankton and macrophytes, indicating a lack of isotopic fractionation during methylation.

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Copyright © 2010. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyAmerican Society of Agronomy, Crop Science Society of America, and Soil Science Society of America