Relationship between mobility factors ( R f) of two hydrophobic termiticides and selected field and artificial soil parameters

Abstract

Mobility of two commonly used hydrophobic termiticides, chlorpyrifos and fenvalerate, was carried out by soil thin layer chromatograph using 3 field soils and 7 artificial soil as absorbent phases. Mobility factors ( R f ) were measured, and single- and multi-variable linear regression equations were then established. The result indicated that chlorpyrifos removed faster than fenvalerate in both field and artificial soils. In field soils negative correlation coefficients ( r) was found between R f and organic matter (OM) content, pH, cationic exchange capacity (CEC), and clay content. It was noticeable, however, that correlation coefficient ( r) derived from single-variable equations were not a reliable criterion for evaluation of relative importance of individual soil parameter in R f determination. One could see, in multi-variable regression, a functional superposition of OM and CEC in pesticide/soil interaction, and the influence of soil pH was overwhelmed by joint action of the other 3 parameters. R f of the two hydrophobic termiticides could therefore be predicted with adequate accuracy by either of the combinations of the two parameter: 1) OM content and clay content, 2) CEC and clay content. Introducing field soil properties into equations established from artificial soils one could see that the four-variable equations, which toke sphagnum as the only source of CEC, gave better prediction of field soil R f . In spite of that these equations were different in two points with those from field soils: Firstly the parameter of soil pH could not be deprived, and secondly, R f of chlorpyrifos was positively correlated with the level of clay content.