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This article in JEQ

  1. Vol. 30 No. 5, p. 1523-1527
    Received: Sept 22, 2000

    * Corresponding author(s): voice@msu.edu


Kinetic Modeling of Bioavailability for Sorbed-Phase 2,4-Dichlorophenoxyacetic Acid

  1. Jeong-Hun Parka,
  2. Denise Kayb,
  3. Xianda Zhaoa,
  4. Stephen A. Boydb and
  5. Thomas C. Voice *a
  1. a Dep. of Civil and Environ. Eng., Michigan State Univ., East Lansing, MI 48824
    b Dep. of Crop and Soil Science, Michigan State Univ., East Lansing, MI 48824


The degradation rate of 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in silica–slurry systems to evaluate the bioavailability of sorbed-phase contaminant. After the silica particles were saturated with 2,4-D, the system was inoculated with the 2,4-D–degrading microorganism Flavorbacterium sp. strain FB4. The disappearance rate of 2,4-D was found to be greater than the rate predicted based upon liquid-phase 2,4-D concentrations. A kinetic formulation, termed the enhanced bioavailability model, was developed to describe the desorption and biodegradation processes in this batch system. The approach assumes that 2,4-D resides in both the liquid and solid phases and degradation occurs via both suspended and attached biomass. All biomass can degrade liquid-phase 2,4-D at one rate, while only attached biomass can degrade sorbed 2,4-D at another rate. An enhanced transformation factor (E f) was introduced to express the increased biodegradation rate over that expected from the liquid phase only. This approach was able to account for the increased degradation rates observed experimentally. The results provide evidence that desorption to the bulk solution is not prerequisite to degradation, and that sorbed substrate may be available for degradation.

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Copyright © 2001. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyPublished in J. Environ. Qual.30:1523–1527.