title: Effects of dissolved organic carbon on sorption and mobility of imidacloprid in soil.
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 degrees 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.
authors.affiliation: Department of Inorganic Chemistry, Univ. of Almería, Spain.
authors.forename: F
authors.initials: F
authors.lastname: Flores-Céspedes
authors.forename: E
authors.initials: E
authors.lastname: González-Pradas
authors.forename: M
authors.initials: M
authors.lastname: Fernández-Pérez
authors.forename: M
authors.initials: M
authors.lastname: Villafranca-Sánchez
authors.forename: M
authors.initials: M
authors.lastname: Socías-Viciana
authors.forename: M D
authors.initials: MD
authors.lastname: Ureña-Amate
mesh_terms: D000327:Adsorption; D002244:Carbon / Q000737:chemistry*; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D047348:Hydrolyzable Tannins / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry*; D007306:Insecticides / Q000737:chemistry*; D000073943:Neonicotinoids; D009574:Nitro Compounds; D010944:Plants; D012987:Soil / Q000032:analysis*; D012989:Soil Pollutants / Q000032:analysis*; D012996:Solutions; D013030:Spain; D014876:Water Pollution / Q000517:prevention & control
chemical_list: D047348:Hydrolyzable Tannins; D007093:Imidazoles; D007306:Insecticides; D000073943:Neonicotinoids; D009574:Nitro Compounds; D012987:Soil; D012989:Soil Pollutants; D012996:Solutions; C082359:imidacloprid; D002244:Carbon