title: Spatial relationships between water quality and pesticide application rates in agricultural watersheds.
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.
authors.affiliation: Department of Environmental Toxicology, University of California, Davis, Marine Pollution Studies Laboratory at Granite Canyon, 34500 Highway 1, Monterey, CA 93940, USA. jwhunt@ucdavis.edu
authors.forename: John W
authors.initials: JW
authors.lastname: Hunt
authors.forename: Brian S
authors.initials: BS
authors.lastname: Anderson
authors.forename: Bryn M
authors.initials: BM
authors.lastname: Phillips
authors.forename: Ron S
authors.initials: RS
authors.lastname: Tjeerdema
authors.forename: Nancy
authors.initials: N
authors.lastname: Richard
authors.forename: Val
authors.initials: V
authors.lastname: Connor
authors.forename: Karen
authors.initials: K
authors.lastname: Worcester
authors.forename: Mark
authors.initials: M
authors.lastname: Angelo
authors.forename: Amanda
authors.initials: A
authors.lastname: Bern
authors.forename: Brian
authors.initials: B
authors.lastname: Fulfrost
authors.forename: Dustin
authors.initials: D
authors.lastname: Mulvaney
mesh_terms: D000383:Agriculture; D002140:California; D004784:Environmental Monitoring / Q000379:methods*; D019015:Geologic Sediments / Q000737:chemistry; D009566:Nitrates / Q000032:analysis; D010575:Pesticides / Q000032:analysis* / Q000592:standards* / Q000633:toxicity; D045483:Rivers / Q000737:chemistry*; D014877:Water Pollution, Chemical / Q000032:analysis*
chemical_list: D009566:Nitrates; D010575:Pesticides