title: Evaluation of sources and loading of pesticides to the Sacramento River, California, USA, during a storm event of winter 2005.
abstract: A monitoring study was conducted in the tributaries and main stem of the Sacramento River, California, USA, during the storm event of January 26 to February 1, 2005. The purpose of the study was to evaluate the sources and loading of pesticides in the Sacramento River watershed during the winter storm season. A total of 26 pesticides or pesticide degradates were analyzed, among which five pesticides and one triazine degradate were detected. Diuron, diazinon, and simazine were found in all streams with a total load of 110.4, 15.4, and 15.7 kg, respectively, in the Sacramento River over the single storm event. Bromacil, hexazinone, and the triazine degradate diaminochlorotriazine were only detected in two smaller drainage canals with a load ranged from 0.25 to 7 kg. The major source of pesticides detected in the main stem Sacramento River was from the most upstream subbasin, the Sacramento River above Colusa, where detected pesticides either exceeded or were close to those at the main outlet of the Sacramento River at Alamar Marina. The higher precipitation in this subbasin was partly responsible for the greater contribution of pesticides observed. Diazinon was the only pesticide with concentrations above water quality criteria, indicating that additional mitigation measures may be needed to reduce its movement to surface water.
authors.affiliation: Department of Pesticide Regulation, Environmental Monitoring Branch, Sacramento, California 95814, USA. lguo@arb.ca.gov
authors.forename: Lei
authors.initials: L
authors.lastname: Guo
authors.forename: Kevin
authors.initials: K
authors.lastname: Kelley
authors.forename: Kean S
authors.initials: KS
authors.lastname: Goh
mesh_terms: D000383:Agriculture; D001976:Bromouracil / Q000031:analogs & derivatives / Q000032:analysis; D002140:California; D004784:Environmental Monitoring; D005843:Geography; D010575:Pesticides / Q000032:analysis*; D011891:Rain; D045483:Rivers / Q000737:chemistry*; D012621:Seasons; D013997:Time Factors; D014227:Triazines / Q000032:analysis; D014481:United States; D014872:Water Movements; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014881:Water Supply / Q000032:analysis*
chemical_list: D010575:Pesticides; D014227:Triazines; D014874:Water Pollutants, Chemical; D001976:Bromouracil; C004590:bromacil; C025641:hexazinone