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Soil Science Society of America Journal Abstract - Wetland Soils

Isotopes Trace Biogeochemistry and Sources of Cu and Zn in an intertidal soil

 

This article in SSSAJ

  1. Vol. 77 No. 2, p. 680-691
     
    Received: July 24, 2012
    Published: February 8, 2013


    * Corresponding author(s): moritz.bigalke@giub.unibe.ch
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doi:10.2136/sssaj2012.0225
  1. Moritz Bigalke *a,
  2. Michael Kerstenb,
  3. Stefan Weyerc and
  4. Wolfgang Wilcked
  1. a Geographic Institute Univ. of Berne Hallerstrasse 12 3012 Berne Switzerland and Johannes Gutenberg-Univ. Mainz Earth System Science Research Center Johann-Joachim-Becher-Weg 21 55128 Mainz Germany
    b Johannes Gutenberg-Univ. Mainz Earth System Science Research Center Johann-Joachim-Becher-Weg 21 55128 Mainz Germany
    c Leibniz Univ. Hannover Institute of Mineralogy Callinstraße 3 30167 Hannover Germany and Univ. of Frankfurt Institute of Geoscience Altenhöferallee 1 60438 Frankfurt am Main Germany
    d Geographic Institute Univ. of Berne Hallerstrasse 12 3012 Berne Switzerland

Abstract

River floodplain soils are sinks and potential sources for toxic trace metals like Cu and Zn. We hypothesize that stable Cu and Zn isotope ratios reflect both the mobilization and the sources of metals. We determined the soil properties, the concentrations and partitioning of Cu and Zn, and variations in δ65Cu and δ66Zn values in a core obtained from an Aquic Udifluvent developed on a freshwater intertidal mudflat of the River Elbe, Germany. The core was sampled at 2 cm intervals to a depth of 34 cm, which corresponds to approximately 9 yr of sedimentation. Elevated concentrations of Cu (up to 320 μg g−1) and Zn (up to 2080 μg g−1) indicated anthropogenic pollution. At the time of sampling the redox conditions changed from oxic (Eh 200 to 400 mV, above 22 cm deep) to strongly anoxic conditions (-100 to -200 mV, below 22 cm deep). The δ65Cu values varied systematically with depth (from -0.02 to 0.16‰) and were correlated with the Fe, C, and N concentrations. Although pre-depositional variations cannot be ruled out, the systematic variation with depth suggests post-sedimentation fractionation of δ65Cu in response to seasonally variable organic matter deposition and redox conditions. In contrast, the δ66ZnIRMM values were uniform (from -0.07 to 0.01‰) throughout the core, indicating that the Zn isotopes did not significantly fractionate after deposition and that the Zn sources were homogeneous throughout the sedimentation.

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