Journal article
Dependence of pesticide degradation on sorption: nonequilibrium model and application to soil reactors
Journal of contaminant hydrology, Vol.43(1), pp.45-62
2000
Handle:
https://hdl.handle.net/2376/114927
Abstract
The effect of sorption on degradation of the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D) was studied in a soil amended with various amounts of activated carbon (AC). The relationship between sorption and decay of 2,4-D was analyzed using analytical solutions for equilibrium sorption and to a two-site nonequilibrium adsorption model coupled with two first-order degradation terms for the dissolved and sorbed pesticide, respectively. The sorption parameters in the latter model were determined based on data obtained from batch sorption experiments, while those for degradation were obtained from incubation experiments. The adsorption coefficients, ranging from 0.811 to >315 ml g
−1, increased at higher AC, and were negatively related to degradation as measured by the first-order rate constant, implying that degradation is faster from the liquid phase than from the sorbed phase. A nonlinear fit of the decay curves to the nonequilibrium model revealed that degradation rate constants were 0.157 and 0.00243 day
−1 for the liquid and sorbed phases, respectively, differing by a factor of 65. Similar results were also obtained using the equilibrium model. A parameter sensitivity analysis of the nonequilibrium model indicates that nonequilibrium sorption will initially favor degradation; however, over the long term, will decrease degradation when desorption kinetics becomes the limiting factor in the degradation process. In the presence of a lag phase that allows appreciable amounts of chemical to diffuse into kinetic sorption sites, nonequilibrium sorption will only impede degradation.
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Details
- Title
- Dependence of pesticide degradation on sorption: nonequilibrium model and application to soil reactors
- Creators
- Lei Guo - Department of Soil and Environmental Sciences, College of Natural and Agricultural Sciences, University of California, Riverside, CA 92521-0424, USAWilliam A Jury - Department of Soil and Environmental Sciences, College of Natural and Agricultural Sciences, University of California, Riverside, CA 92521-0424, USARobert J Wagenet - Department of Soil, Crop and Atmospheric Sciences, Cornell University, Ithaca, NY, USAMarkus Flury - Department of Crop and Soil Sciences, Washington State University, Pullman, Washington, DC, USA
- Publication Details
- Journal of contaminant hydrology, Vol.43(1), pp.45-62
- Academic Unit
- Crop and Soil Sciences, Department of
- Publisher
- Elsevier B.V
- Identifiers
- 99900547611201842
- Language
- English
- Resource Type
- Journal article