PERSISTENCE OF PESTICIDE-RESIDUES IN MINERAL AND ORGANIC SOILS IN THE FRASER VALLEY OF BRITISH-COLUMBIA

In 1989, 12 vegetable farms in the Fraser Valley of British Columbia, Canada, were selected to determine the extent to which pesticide residues were accumulating in the soils. Organochlorine pesticides included BHC (71-899 ppb dry wt), heptachlor (16-614 ppb dry wt), aldrin and dieldrin (78-1280 ppb dry wt), chlordane (170-1800 ppb dry wt), and DDT (194-7162 ppb dry wt). They were found at the higher levels in organic muck soil, at the lower levels in silt loam soil, and were mostly nondetected in loamy sand. Endosulfan and its sulfate (13-14 901 ppb dry wt) were detected consistently in all three soils, and their concentrations were much higher in the muck soil than in the two mineral soils. Residues of organophosphorus and nitrogen-containing pesticides were not found consistently in all three soil types, and their concentrations were generally higher in muck than in mineral soils. Linuron (331-1260 ppb dry wt) was consistently detected in the muck soil and trifluralin (55-310 ppb dry wt) in the loamy sand.