title: An integrated vegetated ditch system reduces chlorpyrifos loading in agricultural runoff.
abstract: Agricultural runoff containing toxic concentrations of the organophosphate pesticide chlorpyrifos has led to impaired water body listings and total maximum daily load restrictions in California's central coast watersheds. Chlorpyrifos use is now tightly regulated by the Central Coast Regional Water Quality Control Board. This study evaluated treatments designed to reduce chlorpyrifos in agricultural runoff. Initial trials evaluated the efficacy of 3 different drainage ditch installations individually: compost filters, granulated activated carbon (GAC) filters, and native grasses in a vegetated ditch. Treatments were compared to bare ditch controls, and experiments were conducted with simulated runoff spiked with chlorpyrifos at a 1.9 L/s flow rate. Chlorpyrifos concentrations and toxicity to Ceriodaphnia dubia were measured at the input and output of the system. Input concentrations of chlorpyrifos ranged from 858 ng/L to 2840 ng/L. Carbon filters and vegetation provided the greatest load reduction of chlorpyrifos (99% and 90%, respectively). Toxicity was completely removed in only one of the carbon filter trials. A second set of trials evaluated an integrated approach combining all 3 treatments. Three trials were conducted each at 3.2 L/s and 6.3 L/s flow rates at input concentrations ranging from 282 ng/L to 973 ng/L. Chlorpyrifos loadings were reduced by an average of 98% at the low flow rate and 94% at the high flow rate. Final chlorpyrifos concentrations ranged from nondetect (<50 ng/L) to 82 ng/L. Toxicity to C. dubia was eliminated in 3 of 6 integrated trials. Modeling of the ditch and its components informed design alterations that are intended to eventually remove up to 100% of pesticides and sediment. Future work includes investigating the adsorption capacity of GAC, costs associated with GAC disposal, and real-world field trials to further reduce model uncertainties and confirm design optimization. Trials with more water-soluble pesticides such as neonicotinoids are also recommended. Integr Environ Assess Manag 2017;13:423-430. © 2016 SETAC.
authors.affiliation: Department of Environmental Toxicology, University of California-Davis, Monterey, California, USA.
authors.forename: Bryn M
authors.initials: BM
authors.lastname: Phillips
authors.affiliation: Department of Environmental Toxicology, University of California-Davis, Monterey, California, USA.
authors.forename: Brian S
authors.initials: BS
authors.lastname: Anderson
authors.affiliation: University of California Cooperative Extension-Monterey County, Salinas, California, USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Cahn
authors.affiliation: Department of Environmental Toxicology, University of California-Davis, Monterey, California, USA.
authors.forename: Jessa L
authors.initials: JL
authors.lastname: Rego
authors.affiliation: Department of Environmental Toxicology, University of California-Davis, Monterey, California, USA.
authors.forename: Jennifer P
authors.initials: JP
authors.lastname: Voorhees
authors.affiliation: Department of Environmental Toxicology, University of California-Davis, Monterey, California, USA.
authors.forename: Katie
authors.initials: K
authors.lastname: Siegler
authors.affiliation: California Department of Pesticide Regulation, Sacramento, California, USA.
authors.forename: Xuyang
authors.initials: X
authors.lastname: Zhang
authors.affiliation: California Department of Pesticide Regulation, Sacramento, California, USA.
authors.forename: Robert
authors.initials: R
authors.lastname: Budd
authors.affiliation: California Department of Pesticide Regulation, Sacramento, California, USA.
authors.forename: Kean
authors.initials: K
authors.lastname: Goh
authors.affiliation: Department of Environmental Toxicology, University of California-Davis, Monterey, California, USA.
authors.forename: Ron S
authors.initials: RS
authors.lastname: Tjeerdema
mesh_terms: D000383:Agriculture; D001673:Biodegradation, Environmental; D004390:Chlorpyrifos / Q000032:analysis*; D052918:Environmental Restoration and Remediation / Q000379:methods*; D007306:Insecticides / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014876:Water Pollution / Q000517:prevention & control*
chemical_list: D007306:Insecticides; D014874:Water Pollutants, Chemical; D004390:Chlorpyrifos
keywords: Agriculture; Aquatic toxicity; Chlorpyrifos; Pesticide; Vegetated treatment system