For decades, state and federal agencies as well as research institutes in California have been collecting water and sediment samples for the purpose of pesticide analysis.  A wealth of monitoring data has been generated and stored in the California Department of Pesticide Regulation’s (CDPR) Surface Water Database (SURF). This study aims to provide a unique comprehensive picture of the occurrence and distribution of pesticides in the surface waters of California. We use various statistical learning methods as well as GIS tools to characterize the spatial and temporal trends of pesticide occurrence in surface water. Important factors associated with the detections of pesticides are explored including pesticide use, dominant land use within the source area, and pesticide physico-chemical properties. Statistical models are used to characterize the relationships of these factors to pesticide detections. The acute and chronic aquatic life benchmarks developed by US EPA are used as a screening tool to derive frequencies of exceedance among various pesticides to allow for a comparison of relative toxicity. The pesticides with the most frequent detections in California surface water are methoxyfenozide, chlorantraniliprole, imidacloprid, fipronil, diazinon, and bifenthrin, among which imidacloprid, fipronil, and bifenthrin had the highest exceedance rate of their respective lowest aquatic life benchmarks. Locations, where these pesticides were monitored and detected, are identified with respective sampling intensity and detection frequency. The results will help guide future monitoring efforts in California regarding where to collect water samples and for what pesticides.<br/>

Pesticides in surface water: A California data story

ACS Fall 2020 Virtual Meeting

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