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This article in JEQ

  1. Vol. 32 No. 6, p. 2207-2215
     
    Received: Nov 4, 2002


    * Corresponding author(s): hdadi@avignon.inra.fr
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doi:10.2134/jeq2003.2207

Modeling of Sorption and Biodegradation of Parathion and Its Metabolite Paraoxon in Soil

  1. K. Saffih-Hdadi *a,
  2. L. Brucklera and
  3. E. Barriusob
  1. a Site Agroparc, Institut National de la Recherche Agronomique, CSE-sol, 84914 Avignon cedex 09, France
    b Institut National Agronomique de Paris-Grignon, EGC-sol, BP 01, 78850 Thiverval-Grignon, France

Abstract

To investigate the distribution of parathion [O,O-diethyl O-(4-nitrophenyl) phosphorothioate] and its highly toxic metabolite paraoxon [O,O-diethyl O-(4-nitrophenyl)phosphate] between the soluble and sorbed pools in the soil, batch experiments were conducted to evaluate the rate of adsorption and desorption of 14C-labeled parathion and paraoxon in soil. The mineralization and degradation of these products were also investigated during a 56-d experiment under controlled laboratory conditions. Adsorption patterns indicated initial fast adsorption reactions occurring within 4 h for both parathion and paraoxon. We also observed the formation of nonextractable residues. The paraoxon was more intensively degraded than the parathion, and production of p-nitrophenol and other metabolites was observed. A kinetic model was developed to describe the sorption and biodegradation rates of parathion, taking into account the production, retention, and biodegradation of paraoxon, the main metabolite of parathion. After fitting the parameters of the model we made a simulation of the kinetics of the appearance and disappearance of paraoxon. From the simulation we predicted a quantity of metabolite in the liquid phase amounting to 1% of the quantity of parathion initially applied. This is in agreement with the experimental data.

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Copyright © 2003. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyASA, CSSA, SSSA