ABSTRACT
The movement of the carbamate insecticide methomyl, S-methyl N-(methyl-carbamoyloxy)thioacetimidate, under steady-state flow was investigated in a small laboratory soil column. This dynamic flow system permitted the simultaneous study of sorption and degradation interactions that occur during transport. The study of methomyl confirms the usefulness of this methodology as a rapid screening tool and further tests the applicability of mathematical models to the description of insecticide movement in soil. Experimental methomyl sorption coefficients agree with literature values from M. Leistra et al. for various soils. Methomyl rapidly decomposes, especially in higher organic carbon contents (OCC) soils, and moves rapidly through lower OCC soils. Methomyl may be more problematic in lower organic content soils, where it is retained to a lesser degree. Thus, ground water contamination by methomyl is more likely in areas with low organic content soils and high precipitation, which would increase methomyl movement through soil and decrease methomyl-soil interactions.
