Prediction and ecotoxicological effects of runoff induced pesticide contamination in agricultural surface waters : a risk assessment using GIS and microcosms

[摘要] ENGLISH ABSTRACT: Runoff is generally regarded as one of the most important routes of nonpoint sourcepesticide pollution in agricultural surface waters. Of major concern is the fact thatlow, sub-lethal levels of pesticide exposure are responsible for negativeecotoxicological effects, stressing the need for methods capable of identifyingproblem areas where populations could be at risk. Predicted average losses of threepesticides in tributaries of nine sub-catchments of the Lourens River were calculatedthrough use of a GIS-based runoff model. There was a significant (p < 0.005) positivecorrelation between the predicted average loss and mean measured concentrations ofthe insecticides both in water and suspended sediments (R2 between 0.75 and 0.9),indicating that the model could serve as a powerful tool for the risk assessment andmanagement of surface waters in South African orchard areas. Based on field relevantexposure scenanos, the potential effects of azinphos-methyl on macroinvertebratecommunities were evaluated in a combined microcosm and field approach.Microcosms were contaminated for 1 h with AZP (control, 0.2; 1,5and 20 ug/L;three replicates each) and acute effects on survival were evaluated 6 days afterexposure. The sensitivity or tolerance of 12 core taxa was determined based on theirresponse to the exposure scenarios and compared to field tolerance/sensitivity as wasestablished by a field investigation at a control and contaminated site of the LourensRiver. The sensitivity/tolerance of ten of the 12 taxa corresponded to that which wasfound in the field. Thus microcosm studies employing a field relevant design can besuccessfully linked to field studies and indicate that transient pesticide contaminationaffects the aquatic communities of the Lourens River.

[发布机构] Stellenbosch University