title: Temporal patterns and sources of atmospherically deposited pesticides in Alpine Lakes of the Sierra Nevada, California, U.S.A.
abstract: Agricultural pesticides are being transported by air large distances to remote mountain areas and have been implicated as a cause for recent population declines of several amphibian species in such locations. Largely unmeasured, however, are the magnitude and temporal variation of pesticide concentrations in these areas, and the relationship between pesticide use and pesticide appearance in the montane environment. We addressed these topics in the southern Sierra Nevada mountains, California, by sampling water weekly or monthly from four alpine lakes from mid-June to mid-October 2003. The lakes were 46-83 km from the nearest pesticide sources in the intensively cultivated San Joaquin Valley. Four of 41 target pesticide analytes were evaluated for temporal patterns: endosulfan, propargite, dacthal, and simazine. Concentrations were very low, approximately 1 ng/L or less, at all times. The temporal patterns in concentrations differed among the four pesticides, whereas the temporal pattern for each pesticide was similar among the four lakes. For the two pesticides applied abundantly in the San Joaquin Valley during the sampling period, endosulfan and propargite, temporal variation in concentrations corresponded strikingly with application rates in the Valley with lag times of 1-2 weeks. A finer-scale analysis suggests that a large fraction of these two pesticides reaching the lakes originated in localized upwind areas within the Valley.
authors.affiliation: National Exposure Research Laboratory, Landscape Ecology Branch, U.S. Environmental Protection Agency, P.O. Box 93478, Las Vegas, Nevada 89193, USA. Bradford.david@epa.gov
authors.forename: David F
authors.initials: DF
authors.lastname: Bradford
authors.forename: Edward M
authors.initials: EM
authors.lastname: Heithmar
authors.forename: Nita G
authors.initials: NG
authors.lastname: Tallent-Halsell
authors.forename: Georges-Marie
authors.initials: GM
authors.lastname: Momplaisir
authors.forename: Charlita G
authors.initials: CG
authors.lastname: Rosal
authors.forename: Katrina E
authors.initials: KE
authors.lastname: Varner
authors.forename: Maliha S
authors.initials: MS
authors.lastname: Nash
authors.forename: Lee A
authors.initials: LA
authors.lastname: Riddick
mesh_terms: D001272:Atmosphere / Q000737:chemistry*; D002140:California; D003510:Cyclohexanes / Q000032:analysis; D017753:Ecosystem; D004726:Endosulfan / Q000032:analysis; D005618:Fresh Water / Q000737:chemistry*; D005843:Geography; D010573:Pesticide Residues / Q000032:analysis*; D010795:Phthalic Acids / Q000032:analysis; D012839:Simazine / Q000032:analysis; D013499:Surface Properties; D013997:Time Factors; D014481:United States
chemical_list: D003510:Cyclohexanes; D010573:Pesticide Residues; D010795:Phthalic Acids; C007220:dimethyl 2,3,5,6-tetrachloroterephthalate; C002771:Omite; D004726:Endosulfan; D012839:Simazine