Adsorption and Mobility of Chlorpyrifos and Fenvalerate in Soils

Adsorption and mobility of two commonly used hydrophobic termiticides,chlorpyrifos and fenvalerate were studied in three soils including Dongqianhu soil (a hillside yellow silty loam),Qingling soil (a yellow spot blue-purple silty loam),and Xiangshan soil (a light sea coast silty clay loam),using batch equilibrium technique and soil thin layer chromatography.The result indicated that Freundlish equations for Dongqianhu soil took a linear form,while the equations for Qingling soil and Xiangshan soil gave a form of "L" shape.Comparison between adsorption coefficient (Kd) and organic carbon correlative adsorption coefficient Koc suggested that adsorption of chlorpyrifos by soils was not only affected by organic matter (OM) but also by clay content,whereas soil adsorption of fenvalerate was affected mainly by OM.From Kd point of view,chlorpyrifos was more strongly adsorbed than fenvalerate by soil components,whereas judged from mobility factors (Rf) chlorpyrifos was more mobile in soils than fevalerate.It suggested that it was not reliable to infer relative mobility among pesticides.Mobility of both chlorpyrifos and fenvalerate in soils was in order of Dongqianhu > Qingling > Xiangshan as scaled by Rf,whereas adsorptive capacity of soils to both chlorpyrifos and fenvalerate was in order of Xiangshan > Qingling > Dongqianhu as scaled by Kd.Single- and multi-variable linear regressive indicated that: 1) There existed a functional superposition of OM and cation exchange capacity (CEC) in their determination of Kd and Rf.2) Either OM and clay content,or CEC and clay content,was necessary and adequate precondition for determination of Kd and Rf.pH of soils was trivial in determination of Kd and Rf.