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

Abstract

16Compound-specific isotope analysis (CSIA) is a powerful tool to track contaminant fate in 17 groundwater. However, the application of CSIA to chlorinated ethanes has received little 18 attention so far. These compounds are toxic and prevalent groundwater contaminants of 19 environmental concern. The high susceptibility of chlorinated ethanes like 20 1,1,1-trichloroethane (1,1,1-TCA) to be transformed via different competing pathways (biotic 21 and abiotic) complicates the assessment of their fate in the subsurface. In this study, the use of 22 a dual C-Cl isotope approach to identify the active degradation pathways of 1,1,1-TCA is 23 This study demonstrates that a dual C-Cl isotope approach can strongly improve the 36 qualitative and quantitative assessment of 1,1,1-TCA degradation processes in the field. 37 38

Understanding Groundwater Mineralization Changes of a Belgian Chalky Aquifer in the Presence of 1,1,1-Trichloroethane Degradation Reactions

“…Local changes in groundwater mineralization have been observed compared to the background composition of groundwater in the aquifer. During the investigations of Palau et al [21], an increase of Ca 2+ , HCO 3 − , Cl − and SO 4 2− was observed within the plume of dissolved CAHs. Sulphate concentrations even exceed the EU drinking water standard (250 mg/L) [22] in some places, reaching concentration levels as high as 5 times the background concentration.…”

Reductive Dehalogenation of Trichloromethane by Two Different Dehalobacter restrictus Strains Reveal Opposing Dual Element Isotope Effects

“… 13 C vs  37 Cl) 26 . The resultant slope =  13 C/ 37 Cl ≈   C/  Cl relates the isotope effects of the two elements to each other and provides a more sensitive parameter to differentiate reaction mechanisms than isotope effects from one element alone [27][28][29][30][31] . An additional advantage of dual element isotope slopes is that they are remarkably insensitive towards masking of intrinsic isotope effects that occurs when the bond breaking reaction is not rate limiting in biocatalysis.…”

Using cell yields and qPCR to estimate biotic contribution to 1,1,1-trichloroethane dechlorination at a field site treated with granular zero valent iron and guar gum

“…In groundwater, 1,1,1-TCA is prone to abiotic transformation to 1,1-dichloroethene (1,1-DCE) via 49 elimination, or to 1,1-dichloroethane (1,1-DCA) via reduction catalyzed either by naturally occurring 50 metals or added metals in engineered systems (Scheutz et al, 2011;Palau et al, 2016). In particular, the 51 addition of zero valent iron (ZVI) has been tested at lab and pilot scales and implemented at various sites 52 to reduce chlorinated compounds including 1,1,1-TCA (Fennell and Roberts, 1998; Agrawal et al, 2002; DCA was often found as the major daughter product and ethane as a minor by-product.…”