title: Constructed wetlands as a component of the agricultural landscape: mitigation of herbicides in simulated runoff from upland drainage areas.
abstract: Constructed wetlands are a recommended practice for buffering pollutant source areas and receiving waters. A wetland consisting of a sediment trap and two treatment cells was constructed in a Mississippi Delta lake watershed. A 3-h simulated runoff event was initiated (2003) to evaluate fate and transport of atrazine and fluometuron through the wetland. Water samples were collected during a runoff simulation and then afterward at selected intervals for 21d, and analyzed for the herbicides. Breakthrough patterns for herbicide concentrations in water samples during the first 20h after simulated runoff showed peak concentrations in the first 6h, with gradual tailing as the herbicide pulse was diluted in the second, excavated (deeper) cell. Atrazine and fluometuron concentrations in the first (shallower, non-excavated) cell averaged 12- and 20-fold greater, respectively, than those in the second cell following simulated runoff, indicating entrapment in the first cell. Atrazine and fluometuron concentrations in the shallower cell decreased 32% and 22%, respectively, 9d following simulated runoff, indicating either degradation or sorption to soil or wetland flora. In the excavated cell, concentrations were even lower, and atrazine declined more rapidly than fluometuron. Results indicate constructed wetlands can improve downstream water quality though sequestration or processing of pollutants.
authors.affiliation: United States Department of Agriculture, Agricultural Research Service, National Sedimentation Laboratory, Water Quality & Ecology Research Unit, 598 McElroy Drive, Oxford, MS 38655, USA. Martin.Locke@ars.usda.gov
authors.forename: M A
authors.initials: MA
authors.lastname: Locke
authors.forename: M A
authors.initials: MA
authors.lastname: Weaver
authors.forename: R M
authors.initials: RM
authors.lastname: Zablotowicz
authors.forename: R W
authors.initials: RW
authors.lastname: Steinriede
authors.forename: C T
authors.initials: CT
authors.lastname: Bryson
authors.forename: R F
authors.initials: RF
authors.lastname: Cullum
mesh_terms: D000383:Agriculture; D001280:Atrazine / Q000032:analysis; D004784:Environmental Monitoring; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005618:Fresh Water / Q000737:chemistry; D006540:Herbicides / Q000032:analysis*; D008782:Methylurea Compounds / Q000032:analysis; D008956:Models, Chemical; D014874:Water Pollutants, Chemical / Q000032:analysis*; D014877:Water Pollution, Chemical / Q000517:prevention & control* / Q000706:statistics & numerical data; D053833:Wetlands
chemical_list: D006540:Herbicides; D008782:Methylurea Compounds; D014874:Water Pollutants, Chemical; C005015:fluometuron; D001280:Atrazine