Spatial Relationships Between Water Quality and Pesticide Application Rates in Agricultural Watersheds |
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Authors: | John W Hunt Brian S Anderson Bryn M Phillips Ron S Tjeerdema Nancy Richard Val Connor Karen Worcester Mark Angelo Amanda Bern Brian Fulfrost Dustin Mulvaney |
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Institution: | (1) Department of Environmental Toxicology, Marine Pollution Studies Laboratory at Granite Canyon, University of California, Davis, 34500 Highway 1, Monterey, CA 93940, USA;(2) California State Water Resources Control Board, 1001 I Street, Sacramento, CA 95814, USA;(3) California Regional Water Quality Control Board, Central Coast Region, 895 Aerovista Place, Suite 101, San Luis Obispo, CA 93401, USA;(4) Department of Environmental Studies, University of California, Santa Cruz, GIS Technology Laboratory, 1156 High Street, Santa Cruz, CA 95064, USA |
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Abstract: | Pesticide applications to agricultural lands in California, USA, are reported to a central data base, while data on water and sediment quality are collected by a number of monitoring programs. Data from both sources are geo-referenced, allowing spatial analysis of relationships between pesticide application rates and the chemical and biological condition of water bodies. This study collected data from 12 watersheds, selected to represent a range of pesticide usage. Water quality parameters were measured during six surveys of stream sites receiving runoff from the selected watershed areas. This study had three objectives: to evaluate the usefulness of pesticide application data in selecting regional monitoring sites, to provide information for generating and testing hypotheses about pesticide fate and effects, and to determine whether in-stream nitrate concentration was a useful surrogate indicator for regional monitoring of toxic substances. Significant correlations were observed between pesticide application rates and in-stream pesticide concentrations (p < 0.05) and toxicity (p < 0.10). In-stream nitrate concentrations were not significantly correlated with either the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.30). Neither total watershed area nor the area in which pesticide usage was reported correlated significantly with the amount of pesticides applied, in-stream pesticide concentrations, or in-stream toxicity (all p > 0.14). In-stream pesticide concentrations and effects were more closely related to the intensity of pesticide use than to the area under cultivation. |
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Keywords: | land use pesticide use reports diazinon chlorpyrifos pyrethroid toxicity Ceriodaphnia dubia Hyalella azteca GIS watershed |
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