EXTRACTABLE AND NONEXTRACTABLE (BOUND) RESIDUES OF ACIFLUORFEN IN AN ORGANIC SOIL

Acifluorfen (AC), -chloro-4-(trifluoromethyl)phenoxy]-2-nitrobenzoic a cid, was applied to an organic soil at 220 mg kg(-1) in a laboratory i ncubation study. A conventional extraction method with solvents and su percritical fluid extraction (SFE) were used to evaluate extractable a nd nonextractable (bound) residues of AC and its metabolites in the so il. Over an incubation period of 7 months, the soil contained 22% AC o f the initially applied herbicide and the residues were almost complet ely extracted with aqueous methanol. Only 0.8% AC was found in the bou nd form. Seventy-five percent AC applied was degraded to aminoacifluor fen (AAC) (due to reduction of nitro group to amino group) of which 60 % was extracted by aqueous methanol, and 15% was in the bound form, ma inly associated with the humin fraction of the soil organic matter. No further transformation of AAC to other metabolites was observed.