WETLANDS AND AQUATIC PROCESSES - DISTRIBUTION AND PERSISTENCE OF AZINPHOS-METHYL AND PARATHION IN CHEMIGATED CRANBERRY BOGS

Ditches draining two cranberry (Vaccinium spp.) bogs flowing into salm on (Oncorhynchus spp.) bearing waterbodies in the Lower Fraser Valley of British Columbia, Canada, were sampled in 1992 to determine the dis tribution and persistence of azinphos-methyl (AZI) and parathion (PAR) following three treatments through an irrigation system (chemigation) , to control the black-headed fireworm (Rhopobota naevana Hbn), One bo g was surrounded by a secured dike system for water retention and the other by a leaking dike system, representing a worst-case scenario. Af ter each treatment, AZI and PAR residues were detected in ditch water (detection limit = 0.05 mu g/L) and sediments (detection limit = 5 mu g/kg) inside and outside the bogs and they persisted for 72 and 32 d, respectively. The highest concentrations in water were 175 mu g/L for AZI and 21 mu g/L for PAR, Concentrations of AZI and PAR in sediments ranged from not detected to 1582 mu g/kg and persisted for 210 and 13 d, respectively, Low levels of aerial drift resulting from the treatme nt were detected beyond the outer perimeter of the sprinkler irrigatio n system in the cranberry bogs. Off-site release of insecticide residu es occurred in the leaking dike system but not in the secured dike sys tem, The released insecticide residues adversely affected nontarget aq uatic organisms, Harvested cranberries contained no detectable (detect ion limit = 5 mu g/kg) residues of AZI and PAR.