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This article in JEQ

  1. Vol. 24 No. 1, p. 183-190
    Received: Nov 15, 1993

    * Corresponding author(s):
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Speciation of Cadmium and Zinc with Application to Soil Solutions

  1. P. E. Holm *,
  2. T. H. Christensen,
  3. J. C. Tjell and
  4. S. P. McGrath
  1. Soil Sci. Dep., Inst. of Arable Crops Res., Rothamsted Exp. Stn., Harpenden, Herts AL5 2JQ, UK.



A two-part method has been developed for determination of Cd and Zn species in 50-mL soil solution samples containing low concentrations of Cd and Zn (1–10 μg Cd L−1 and 50–1000 μg Zn L−1). The method uses two cation exchange resins (Amberlite CG 120 and Chelex 100) in a batch-column-batch procedure and relies on analytical determinations of Cd and Zn by graphite furnace atomic absorption spectrophotometry. The first part (batch) of the method allows determination of free divalent Cd2+ and Zn2+. This part is experimentally sensitive to cation concentrations and ionic strength and these parameters should be controlled during the experimental procedures. However, it is shown that Cd and Zn concentrations and pH do not influence the method. Speciations performed on samples containing chloride and sulfate were in accordance with theoretical calculations. The second part (column-batch) of the method operationally separates the complexed fraction into labile complexes, slowly labile complexes, and stable complexes. Chloro complexes were identified as labile complexes, while EDTA complexes were identified as stable complexes. The method works well with relatively small volumes of sample solutions and at low metal concentrations and may be useful in characterization of Cd and Zn in soil solutions.

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