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Water Res

Title:		"Use of dual carbon-chlorine isotope analysis to assess the degradation pathways of 1,1,1-trichloroethane in groundwater"
Author(s):		Palau J; Jamin P; Badin A; Vanhecke N; Haerens B; Brouyere S; Hunkeler D;
Address:		"University of Neuchatel, Centre for Hydrogeology and Geothermics (CHYN), Building UniMail, Rue Emile-Argand 11, 2000 Neuchatel, Switzerland; Institute of Environmental Assessment and Water Research (IDAEA), CSIC, Jordi Girona 18-26, Barcelona 08034, Spain. Electronic address: jordi.palau@ub.edu. University of Liege, Fac. Applied Sciences, Dpt ArGEnCo, Geo(3)-Hydrogeology and Environmental Geology, Building B52, 4000 Sart-Tilman, Belgium. University of Neuchatel, Centre for Hydrogeology and Geothermics (CHYN), Building UniMail, Rue Emile-Argand 11, 2000 Neuchatel, Switzerland. AECOM, Maria-Theresiastraat 34A, 3000 Leuven, Belgium"
Journal Title:		Water Res
Year:		2016
Volume:		20160202
Issue:
Page Number:		235 - 243
DOI:		10.1016/j.watres.2016.01.057
ISSN/ISBN:		1879-2448 (Electronic) 0043-1354 (Linking)
Abstract:		"Compound-specific isotope analysis (CSIA) is a powerful tool to track contaminant fate in groundwater. However, the application of CSIA to chlorinated ethanes has received little attention so far. These compounds are toxic and prevalent groundwater contaminants of environmental concern. The high susceptibility of chlorinated ethanes like 1,1,1-trichloroethane (1,1,1-TCA) to be transformed via different competing pathways (biotic and abiotic) complicates the assessment of their fate in the subsurface. In this study, the use of a dual C-Cl isotope approach to identify the active degradation pathways of 1,1,1-TCA is evaluated for the first time in an aerobic aquifer impacted by 1,1,1-TCA and trichloroethylene (TCE) with concentrations of up to 20 mg/L and 3.4 mg/L, respectively. The reaction-specific dual carbon-chlorine (C-Cl) isotope trends determined in a recent laboratory study illustrated the potential of a dual isotope approach to identify contaminant degradation pathways of 1,1,1-TCA. Compared to the dual isotope slopes (Deltadelta(13)C/Deltadelta(37)Cl) previously determined in the laboratory for dehydrohalogenation/hydrolysis (DH/HY, 0.33 +/- 0.04) and oxidation by persulfate (infinity), the slope determined from field samples (0.6 +/- 0.2, r(2) = 0.75) is closer to the one observed for DH/HY, pointing to DH/HY as the predominant degradation pathway of 1,1,1-TCA in the aquifer. The observed deviation could be explained by a minor contribution of additional degradation processes. This result, along with the little degradation of TCE determined from isotope measurements, confirmed that 1,1,1-TCA is the main source of the 1,1-dichlorethylene (1,1-DCE) detected in the aquifer with concentrations of up to 10 mg/L. This study demonstrates that a dual C-Cl isotope approach can strongly improve the qualitative and quantitative assessment of 1,1,1-TCA degradation processes in the field"
Keywords:		"Carbon Isotopes Chlorine/*chemistry Groundwater/*chemistry Halogenation Hydrocarbons/analysis Isotope Labeling/*methods Trichloroethanes/*chemistry Trichloroethylene/analysis Water Pollutants, Chemical/analysis Abiotic degradation Chlorinated solvents Com;"
Notes:		"MedlinePalau, Jordi Jamin, Pierre Badin, Alice Vanhecke, Nicolas Haerens, Bruno Brouyere, Serge Hunkeler, Daniel eng Research Support, Non-U.S. Gov't England 2016/02/14 Water Res. 2016 Apr 1; 92:235-43. doi: 10.1016/j.watres.2016.01.057. Epub 2016 Feb 2"