title: Experimental dosing of wetlands with coagulants removes mercury from surface water and decreases mercury bioaccumulation in fish.
abstract: Mercury pollution is widespread globally, and strategies for managing mercury contamination in aquatic environments are necessary. We tested whether coagulation with metal-based salts could remove mercury from wetland surface waters and decrease mercury bioaccumulation in fish. In a complete randomized block design, we constructed nine experimental wetlands in California's Sacramento-San Joaquin Delta, stocked them with mosquitofish (Gambusia affinis), and then continuously applied agricultural drainage water that was either untreated (control), or treated with polyaluminum chloride or ferric sulfate coagulants. Total mercury and methylmercury concentrations in surface waters were decreased by 62% and 63% in polyaluminum chloride treated wetlands and 50% and 76% in ferric sulfate treated wetlands compared to control wetlands. Specifically, following coagulation, mercury was transferred from the filtered fraction of water into the particulate fraction of water which then settled within the wetland. Mosquitofish mercury concentrations were decreased by 35% in ferric sulfate treated wetlands compared to control wetlands. There was no reduction in mosquitofish mercury concentrations within the polyaluminum chloride treated wetlands, which may have been caused by production of bioavailable methylmercury within those wetlands. Coagulation may be an effective management strategy for reducing mercury contamination within wetlands, but further studies should explore potential effects on wetland ecosystems.
authors.affiliation: †U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, California 95620, United States.
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Ackerman
authors.affiliation: ‡U.S. Geological Survey, California Water Science Center, 6000 J Street, Placer Hall, Sacramento, California 95819, United States.
authors.forename: Tamara E C
authors.initials: TE
authors.lastname: Kraus
authors.affiliation: ‡U.S. Geological Survey, California Water Science Center, 6000 J Street, Placer Hall, Sacramento, California 95819, United States.
authors.forename: Jacob A
authors.initials: JA
authors.lastname: Fleck
authors.affiliation: §U.S. Geological Survey, Wisconsin District, 8505 Research Way, Middleton, Wisconsin 53562, United States.
authors.forename: David P
authors.initials: DP
authors.lastname: Krabbenhoft
authors.affiliation: ⊥University of California, Davis, Department of Land, Air, and Water Resources, Davis, California 95616, United States.
authors.forename: William R
authors.initials: WR
authors.lastname: Horwath
authors.affiliation: ∥Bachand and Associates, 2023 Regis Drive, Davis, California 95616, United States.
authors.forename: Sandra M
authors.initials: SM
authors.lastname: Bachand
authors.affiliation: †U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, California 95620, United States.
authors.forename: Mark P
authors.initials: MP
authors.lastname: Herzog
authors.affiliation: †U.S. Geological Survey, Western Ecological Research Center, Dixon Field Station, 800 Business Park Drive, Suite D, Dixon, California 95620, United States.
authors.forename: C Alex
authors.initials: CA
authors.lastname: Hartman
authors.affiliation: ∥Bachand and Associates, 2023 Regis Drive, Davis, California 95616, United States.
authors.forename: Philip A M
authors.initials: PA
authors.lastname: Bachand
mesh_terms: D000818:Animals; D002140:California; D003029:Coagulants; D052918:Environmental Restoration and Remediation / Q000379:methods*; D005399:Fishes; D008628:Mercury / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification*; D008767:Methylmercury Compounds / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry / Q000302:isolation & purification*; D053833:Wetlands
chemical_list: D003029:Coagulants; D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D008628:Mercury