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This article in JEQ

  1. Vol. 31 No. 3, p. 880-888
     
    Received: May 31, 2001
    Published: May, 2002


    * Corresponding author(s): egonzale@ual.es
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doi:10.2134/jeq2002.8800

Effects of Dissolved Organic Carbon on Sorption and Mobility of Imidacloprid in Soil

  1. F. Flores-Céspedes,
  2. E. González-Pradas *,
  3. M. Fernández-Pérez,
  4. M. Villafranca-Sánchez,
  5. M. Socías-Viciana and
  6. M.D. Ureña-Amate
  1. Department of Inorganic Chemistry, Univ. of Almería, La Cañada de San Urbano s/n, 04120, Almería, Spain

Abstract

To evaluate the effects of dissolved organic carbon on sorption and mobility of the insecticide imidacloprid [1-(6-chloro-3-pyridinyl) methyl-N-nitro-2-imidazolidinimine] in soils, adsorption and column experiments were performed by using a typical calcareous soil from southeastern Spain and two different types of dissolved organic carbon, that is, dissolved organic carbon extracts from a commercial peat (DOC-PE) and high-purity tannic acid (DOC-TA). The experiments were carried out from a 0.01 M CaCl2 aqueous medium at 25°C. The results obtained from the sorption experiments show that the presence of both DOC-PE and DOC-TA, over a concentration range of 15 to 100 mg L−1, produces in all cases a decreasing amount of imidacloprid adsorbed in the soil studied. From the column experiments the retardation coefficients (RC) were calculated for imidacloprid by using either 0.01 M CaCl2 aqueous solution (RC = 2.10), 0.01 M CaCl2 DOC-PE solution (RC = 1.65), or 0.01 M CaCl2 DOC-TA solution (RC = 1.87). The results indicate that mobility of imidacloprid is increased 21.4 and 11.0% in the presence of DOC-PE and DOC-TA solutions, respectively. Dissolved organic carbon reduces imidacloprid sorption by competing with the pesticide molecules for sorption sites on the soil surface, allowing enhanced leaching of imidacloprid and potentially increasing ground water contamination.

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Copyright © 2002. American Society of Agronomy, Crop Science Society of America, Soil Science SocietyPublished in J. Environ. Qual.31:880–888.