Detection and Degradation of Linuron in Organic Soils

Abstract

Detection and degradation of linuron [3-(3,4-dichlorophenyl) -1 - methoxy -1 - methylurea] in organic soils were studied using biological assays and chromatographic techniques. The level of linuron that caused 50% growth reduction of onion (Allium cepa L.) varied among three soils of greatly differing organic matter contents. Linuron and its metabolites were successfully separated with florisil column chromatography using a five-fraction solvent system; however, only linuron and 3 - (3,4 - dichlorophenyl) -1 -methylurea could be extracted from organic soil samples at satisfactory recovery rates. Soil samples from eight grower fields and from field plots were analyzed to determine the residue level of these two compounds. Quantitative assessment of the compounds was made with high pressure liquid chromatography. Results of the biological assay and chromatographic analysis showed that linuron and its phytotoxic metabolite, 3 - (3,4 - dichlorophenyl) -1 - methylurea, were not accumulating in the organic soils of Ontario and that the levels detected were not phytotoxic to onions when grown in pot bioassays.