Conversion and leaching of aldicarb in soil columns

Aldicarb was applied to soil columns in the laboratory which were leached by artificial rainfall. Concentrations of aldicarb, its sulphoxide and its sulphone in the effluent were measured by gas‐liquid chromatography. The measured results were analysed in some detail using a computation model. Aldicarb and its oxidation products were very mobile in soil, a fact which could be well described after introducing very low sorption coefficients in the computation model. Aldicarb itself was converted at a high rate following first order kinetics (half‐life about 2 days). The best approximations obtained for the rate constant of sulphoxide conversion in two soils were about 0.03 and 0.06/day respectively (half‐lives 23 and 12 days). Only a rather wide range of possible values could be obtained for the rate at which sulphone was decomposed.