Cl and C isotope analysis to assess the effectiveness of chlorinated ethene degradation by zero-valent iron: Evidence from dual element and product isotope values

Carbon and Chlorine Isotope Analysis to Identify Abiotic Degradation Pathways of 1,1,1-Trichloroethane

“…Interestingly, the product isotope pattern for 1,1,1-TCA is different than that observed during reduction of TCE by Fe(0) in previous studies. 46,59 Contrary to reduction of 1,1,1-TCA, ethene/ethane produced from TCE were constantly depleted in 13 C (about 10‰) compared to the hydrogenolysis product (cisdichloroethylene). The difference between the product isotope patterns of TCE and 1,1,1-TCA could be due to distinct reaction mechanisms leading to formation of ethene/ethane.…”

“…The occurrence of distinct mechanisms is supported by previous studies indicating that production of ethene/ethane from TCE mainly proceeds via β-dichloroelimination to chloroacetylene. 46,60 For the Fe(0) pathway, an ε bulk C of −13.6 ± 0.5‰ from a previous study is available for comparison. 36 This value is larger than the one determined in our study (−7.8 ± 0.4‰), however, significant variation ranging from −10.3 to −14.0‰ has also been recently observed during reduction of 1,1,1-TCA by biotically mediated FeS formation in microcosm experiments.…”

Identification of abiotic and biotic reductive dechlorination in a chlorinated ethene plume after thermal source remediation by means of isotopic and molecular biology tools

“…1. Literature values for dual C\ \Cl isotope slopes associated with various degradation pathways of chlorinated ethenes (Abe et al, 2009;Audí-Miró et al, 2013;Cretnik et al, 2013;Kuder et al, 2013;Badin et al, 2014;Cretnik et al, 2014;Renpenning et al, 2014). Slopes are given for each of the substrates.…”

“…It was demonstrated that the extent of biodegradation could be determined based on isotopic measurements (Hunkeler et al, 2010). Additionally, it was suggested that dual C\ \Cl isotopic analysis may help to differentiate degradation pathways, for example biotic from abiotic degradation (Elsner et al, 2005;Abe et al, 2009;Audí-Miró et al, 2013) despite some limitations (Badin et al, 2014;Renpenning et al, 2014). The range of laboratory determined dual C\ \Cl isotope slopes associated with various chlorinated ethene degradation processes has increased in recent years, thus enriching the database to which dual C\ \Cl isotope slopes measured in the field can be compared for process identification ( Fig.…”

“…The range of laboratory determined dual C\ \Cl isotope slopes associated with various chlorinated ethene degradation processes has increased in recent years, thus enriching the database to which dual C\ \Cl isotope slopes measured in the field can be compared for process identification ( Fig. 1) (Abe et al, 2009;Audí-Miró et al, 2013;Kuder et al, 2013;Wiegert et al, 2013;Badin et al, 2014;Cretnik et al, 2014;Renpenning et al, 2014). Moreover, rapid advances in molecular biology open new possibilities for the characterization of microbial communities present in the subsurface and the assessment of their activity based on mRNA analysis.…”