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This article in SSSAJ

  1. Vol. 56 No. 4, p. 1004-1015
    Received: July 31, 1991

    * Corresponding author(s):
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Modeling the Transport and Retention of Cadmium in Soils: Multireaction and Multicomponent Approaches

  1. H. M. Selim ,
  2. B. Buchter,
  3. C. Hinz and
  4. L. Ma
  1. Agronomy Dep., Louisiana State Univ., Baton Rouge, LA 70803



A major challenge in modeling the mobility of solutes in soils is to take into account the time- dependent retention of reactive solutes in a transport model that can be evaluated by independent experiments. The kinetics of retention and transport of Cd in two soils were investigated in this study. Time-dependent batch experiments were carried out to describe the extent of Cd sorption by two soils. Miscible-displacement experiments were conducted to quantify Cd transport in soil columns that received single and multiple Cd pulses. A multi-reaction convective-dispersive transport model inadequately predicted effluent concentrations for both soils when independently measured parameters of retention-release rate coefficients were obtained from batch data sets. We developed a multicomponent approach that accounts for reversible and irreversible Cd retention during transport in soils. Retention mechanisms considered include instantaneous equilibrium ion exchange and a specific sorption process that was based on a second-order (Langmuir) kinetic reaction. The multicomponent model adequately predicted the observed breakthrough results. The use of kinetic ion exchange and specific sorption for irreversible retention provided improved overall predictions of the results. Parameter values used for the rates of specific sorption (kt) and that for kinetic ion exchange (α), which provided improved predictions for single-pulse applications, were similar to those used for multiple-pulse applications. This finding was consistent for both soils and was considered to add credence to our multicomponent model.

Manuscript no. 92-09-6002 of the Louisiana Agric. Exp. Stn.

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