Abstract

In 1991 a study of two urban streams in Hamilton and two urban stormwater detention ponds in Guelph was initiated to determine the degree of pesticide contamination in these systems. Water was tested for phenoxy acid herbicides (i.e. 2,4-D, mecoprop, dicamba, MCPA), for neutral herbicides (i.e. trifluralin, atrazine, metolachlor), and for organophosphorus insecticides (i.e. diazinon, dimethoate, chlorpyrifos), during base flow and during runoff events. Sediment was collected and analyzed for persistent organochlorine compounds and for selected pesticides. A questionnaire was circulated to the residents of two Guelph subdivisions to determine the types and amounts of pesticide used by householders.

Canadian Water Quality Guidelines (CWQG) for Drinking Water were not exceeded for any of the pesticides. Concentrations of 2,4-D did exceed the CWQG for the Protection of Freshwater Aquatic Life in 10% of the samples collected. The maximum observed concentration of 2,4-D was 14.6,ug/L, more than three times the CWQG for the Protection of Freshwater Aquatic Life (4 ?g/ L). Eight other phenoxy acid herbicides were also detected. The organophosphorus (OP) insecticides diazinon, dimethoate, and chlorpyrifos, were detected in water. Although provincial (Ontario) water quality objectives exist for some of the OPs there are no CWQGs for the Protection of Freshwater Aquatic Life for OPs. The neutral herbicides atrazine, metolachlor, and trifluralin, were also detected in water. Eight persistent organochlorines and atrazine were detected in sediment samples. Survey results indicated that in 1991 over twenty different pesticide compounds were used in the study areas. 66% of the lawns and/or gardens in the two subdivisions received at least one pesticide application and 36% of the homes used a professional lawn care service.

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