Use of dual carbon-chlorine isotope analysis to assess the degradation pathways of 1,1,1-trichloroethane in groundwater

WATER RESEARCH

卷:92

Article

Palau, Jordi^1,4  Jamin, Pierre²  Badin, Alice¹  Vanhecke, Nicolas³  Haerens, Bruno³  Brouyere, Serge²  Hunkeler, Daniel¹ 

[1] Univ Neuchatel, Ctr Hydrogeol & Geotherm CHYN, Bldg UniMail,Rue Emile Argand 11, CH-2000 Neuchatel, Switzerland

[2] Univ Liege, Fac Sci Appl, Dpt ArGEnCo, Hydrogeol & Environm Geol Geo3, Bldg B52, B-4000 Sart Tilman Par Liege, Belgium

[3] AECOM, Maria Theresiastr 34A, B-3000 Leuven, Belgium

[4] CSIC, Inst Environm Assessment & Water Res IDAEA, Jordi Girona 18-26, ES-08034 Barcelona, Spain

关键词: Volatile organic contaminants;    Chlorinated solvents;    Compound-specific isotope analysis;    Contaminant fate;    Groundwater remediation;    Abiotic degradation;   

DOI  :  10.1016/j.watres.2016.01.057

来源: Elsevier

【 摘 要 】

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 (Delta delta C-13/Delta delta Cl-37) 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. (C) 2016 Elsevier Ltd. All rights reserved.

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