title: Field demonstration of DNAPL dehalogenation using emulsified zero-valent iron.
abstract: This paper describes the results of the first field-scale demonstration conducted to evaluate the performance of nanoscale emulsified zero-valent iron (EZVI) injected into the saturated zone to enhance in situ dehalogenation of dense, nonaqueous phase liquids (DNAPLs) containing trichloroethene (TCE). EZVI is an innovative and emerging remediation technology. EZVI is a surfactant-stabilized, biodegradable emulsion that forms emulsion droplets consisting of an oil-liquid membrane surrounding zero-valent iron (ZVI) particles in water. EZVI was injected over a five day period into eight wells in a demonstration test area within a larger DNAPL source area at NASA's Launch Complex 34 (LC34) using a pressure pulse injection method. Soil and groundwater samples were collected before and after treatment and analyzed for volatile organic compounds (VOCs) to evaluate the changes in VOC mass, concentration and mass flux. Significant reductions in TCE soil concentrations (>80%) were observed at four of the six soil sampling locations within 90 days of EZVI injection. Somewhat lower reductions were observed at the other two soil sampling locations where visual observations suggest that most of the EZVI migrated up above the target treatment depth. Significant reductions in TCE groundwater concentrations (57 to 100%) were observed at all depths targeted with EZVI. Groundwater samples from the treatment area also showed significant increases in the concentrations of cis-1,2-dichloroethene (cDCE), vinyl chloride (VC) and ethene. The decrease in concentrations of TCE in soil and groundwater samples following treatment with EZVI is believed to be due to abiotic degradation associated with the ZVI as well as biodegradation enhanced by the presence of the oil and surfactant in the EZVI emulsion.
authors.affiliation: National Aeronautics and Space Administration, Mail Stop YA-C3-C, Kennedy Space Center, Florida 32899, USA. Jacqueline.W.Quinn@nasa.gov
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Quinn
authors.forename: Cherie
authors.initials: C
authors.lastname: Geiger
authors.forename: Chris
authors.initials: C
authors.lastname: Clausen
authors.forename: Kathleen
authors.initials: K
authors.lastname: Brooks
authors.forename: Christina
authors.initials: C
authors.lastname: Coon
authors.forename: Suzanne
authors.initials: S
authors.lastname: O'Hara
authors.forename: Thomas
authors.initials: T
authors.lastname: Krug
authors.forename: David
authors.initials: D
authors.lastname: Major
authors.forename: Woong-Sang
authors.initials: WS
authors.lastname: Yoon
authors.forename: Arun
authors.initials: A
authors.lastname: Gavaskar
authors.forename: Thomas
authors.initials: T
authors.lastname: Holdsworth
mesh_terms: D001673:Biodegradation, Environmental; D004655:Emulsions; D007501:Iron / Q000737:chemistry*; D036103:Nanotechnology; D012989:Soil Pollutants / Q000302:isolation & purification*; D012997:Solvents / Q000737:chemistry* / Q000302:isolation & purification*; D013501:Surface-Active Agents; D014241:Trichloroethylene / Q000737:chemistry* / Q000302:isolation & purification*; D014873:Water Pollutants / Q000302:isolation & purification*
chemical_list: D004655:Emulsions; D012989:Soil Pollutants; D012997:Solvents; D013501:Surface-Active Agents; D014873:Water Pollutants; D014241:Trichloroethylene; D007501:Iron