Off-site transport of pesticides from two horticultural land uses in the Mt. Lofty Ranges, South Australia

Abstract

Abstract Local runoff from the catchments in the Mt. Lofty Ranges provides a major source of drinking water for the city of Adelaide, South Australia, Australia. In this study two major land uses (apples and cherries) in the Mt. Lofty Ranges were monitored for off-site transport of pesticides over approximately 30 months. While fungicides have been rarely reported in the literature to be present in surface water, in our studies several fungicides (fenarimol, bupirimate, penconazole, procymidone, propiconazole) were found to be transported off-site in a persistent manner over the study period. Two pesticides (chlorpyrifos and fenarimol) from the apple orchard were of particular concern. The average chlorpyrifos concentrations in 2007 and 2009 were more than ten times the environmental guideline value (0.01 μg/L), suggesting potential deleterious effects on aquatic organisms immediately downstream of the apple orchard. Fenarimol was detected in 19 water samples collected from early April to early June 2007 and in 95% of these cases the total concentration exceeded the Australian Drinking Water Quality Guideline (no environmental guidelines are available in Australia for this chemical). For pesticides such as chlorpyrifos and fenarimol at least a ten-fold dilution would be required in the receiving environment for the concentrations to be below current guideline values. Generally more pesticides were detected in drainage water leaving the apple orchard than the cherry orchard, reflecting higher pesticide use at the former. The results from this study indicate that pesticides are of concern in this catchment and strategies for minimising off-site transport need to be developed and evaluated. Data from this study show that while some pesticides move off-site predominantly with the first runoff event some pesticides continue to be transported off-site for months. Some pesticides in the Mt. Lofty Ranges are persisting in soils or on the crop canopy for considerable time periods and being detected in surface runoff water months after the last application.