Persistence and degradation of coumaphos in model cattle dipping vats

The stability of coumaphos [O,O-diethyl O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7 yl)phosphorothioatel was studied in model dipping vats under field conditions using 14C-labelled and unlabelled coumaphos, with or without additives. The stability of coumaphos in model vats increased significantly by maintaining a pH of 5 by addition of superphosphate. Copper sulphate amendment did not seem to have any additional effect on stability. Potasan was the major metabolite in addition to chlorferon and 4-methylumbelliferone. Coumaphos concentration was doubled in the sediment of vat treated with copper sulphate as compared to the control vat as a result of emulsion breakdown. Chlorferon was the only metabolite detected in the sediment of the former vat indicating inhibition of the anaerobic degradation.