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

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 (Rf) 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 Rf 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 Rf 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. Rf 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 Rf. 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, Rf of chlorpyrifos was positively correlated with the level of clay content.