DEGRADATION OF ALACHLOR IN CHIRONOMID LARVAE (DIPTERA, CHIRONOMIDAE)

Field-collected chironomid larvae were placed in 2-mL sterile water solutions containing 4.5 ppm unlabeled or C-14-labeled alachlor. Within 1 h, the alachlor was assimilated into the larvae to a 7-10-fold concentration. The rate of disappearance of alachlor from aqueous solution was measured with gas chromatography. Within 17 h, 83 % of the alachlor was gone from the water. Alachlor metabolites were isolated by high-performance liquid chromatography or thin-layer chromatography and were identified by thin-layer chromatography or mass spectroscopy. The major metabolite returning to the water was tentatively identified as the O-demethylated derivative of alachlor. The metabolites CDEPA and DEA were also identified. An additional unidentified metabolite was found in the larvae at high levels. Differences in the metabolites found in the water versus the insect tissue may be important when considering the actual levels of alachlor in the aquatic ecosystem and the ultimate fate of alachlor in the environment.