Use of dual carbon-chlorine isotope analysis to assess the degradation pathways of 1,1,1-trichloroethane in groundwater
Jordi Palau Capdevila, Pierre Jamin, Alice Badin, Nicolas Vanhecke, Bruno Haerens, Serge Brouyère & Daniel Hunkeler
| Résumé |
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.
Thesecompounds are toxic and prevalent groundwater contaminants of
environmental concern. The highsusceptibility of chlorinated
ethanes like 1,1,1-trichloroethane (1,1,1-TCA) to be transformed
via differentcompeting pathways (biotic and abiotic) complicates
the assessment of their fate in the subsurface. Inthis study, the
use of a dual CeCl isotope approach to identify the active
degradation pathways of 1,1,1-TCA is evaluated for thefirst 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 carbonechlorine (CeCl)
isotope trends determined in a recent laboratory study illustrated
the potential of adual isotope approach to identify contaminant
degradation pathways of 1,1,1-TCA. Compared to the dualisotope
slopes (Dd13C/Dd37Cl) previously determined in the laboratory for
dehydrohalogenation/hydro-lysis (DH/HY, 0.33±0.04) and oxidation by
persulfate (∞), the slope determined fromfield
samples(0.6±0.2, r2¼0.75) is closer to the one observed for DH/HY,
pointing to DH/HY as the predominantdegradation pathway of
1,1,1-TCA in the aquifer. The observed deviation could be explained
by a minorcontribution of additional degradation processes. This
result, along with the little degradation of TCEdetermined 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 studydemonstrates that a dual
CeCl isotope approach can strongly improve the qualitative and
quantitativeassessment of 1,1,1-TCA degradation processes in the
field. |
| Mots-clés |
Volatile organic contaminants; Chlorinated solvents; Compound-specific isotope analysis; Contaminant fate; Groundwater remediation; Abiotic degradation |
| Citation | Palau Capdevila, J., Jamin, P., Badin, A., Vanhecke, N., Haerens, B., Brouyère, S., & Hunkeler, D. (2016). Use of dual carbon-chlorine isotope analysis to assess the degradation pathways of 1,1,1-trichloroethane in groundwater. Water Research, 92, 235-243. |
| Type | Article de périodique (Anglais) |
| Date de publication | 2-2016 |
| Nom du périodique | Water Research |
| Volume | 92 |
| Pages | 235-243 |
| URL | http://dx.doi.org/10.1016/j.watres.2016.01.057 |