title: Nonbiological removal of cis-dichloroethylene and 1,1-dichloroethylene in aquifer sediment containing magnetite.
abstract: The U.S. EPA Technical Protocol for Evaluating Natural Attenuation of Chlorinated Solvents in Groundwater emphasizes biological reductive dechlorination as the primary mechanism for destruction of chlorinated solvents. However, biological reductive dechlorination could not explain the removal of cis-dichloroethylene (cis-DCE) and 1,1-DCE from a plume of contaminated groundwater in Minnesota. Several recent laboratory studies have demonstrated that common iron minerals such as magnetite can also transform chlorinated alkenes. Laboratory microcosms were constructed with sediment from three depth intervals in the aquifer near the source of the plume. The microcosms were autoclaved to prevent biological transformations. In these autoclaved sediments, the rates of removal of cis-DCE in samples from the shallow, intermediate, and deeper depth intervals in the aquifer were 0.58 +/- 0.09, 2.29 +/- 0.26, and 0.31 +/- 0.08 per year at 95% confidence. The rate of removal of 1,1-DCE in sediment from the shallow interval was 1.37 +/- 0.50 per year. The rates of removal in the microcosms are similar to the rates of attenuation observed in the field. Magnetite was identified in the sediment by X-ray diffraction and optical microscopy. Published rates of transformation of cis-DCE by magnetite are consistent with the rates of removal in the microcosm study.
authors.affiliation: Minnesota Pollution Control Agency, 520 Lafayette Road, St. Paul, Minnesota 55155-4194, USA. mark.ferrey@pca.state.mn.us
authors.forename: Mark L
authors.initials: ML
authors.lastname: Ferrey
authors.forename: Richard T
authors.initials: RT
authors.lastname: Wilkin
authors.forename: Robert G
authors.initials: RG
authors.lastname: Ford
authors.forename: John T
authors.initials: JT
authors.lastname: Wilson
mesh_terms: D004000:Dichloroethylenes / Q000737:chemistry / Q000302:isolation & purification*; D052203:Ferrosoferric Oxide; D019015:Geologic Sediments / Q000737:chemistry; D007501:Iron / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D012989:Soil Pollutants / Q000032:analysis; D012997:Solvents / Q000737:chemistry / Q000302:isolation & purification*; D014873:Water Pollutants / Q000032:analysis
chemical_list: D004000:Dichloroethylenes; D010087:Oxides; D012989:Soil Pollutants; D012997:Solvents; D014873:Water Pollutants; D007501:Iron; D052203:Ferrosoferric Oxide