C and Cl isotope fractionation of 1,2-dichloroethane displays unique δ13C/δ37Cl Patterns for Pathway Identification and Reveals Surprising C-Cl bond involvement in microbial oxidation

Jordi Palau, Stefan Cretnik, Orfan Shouakar-Stash, Martina Höche, Martin Elsner, Daniel Hunkeler

Research output: Contribution to journalArticlepeer-review

48 Scopus citations

Abstract

This study investigates dual element isotope fractionation during aerobic biodegradation of 1,2-dichloroethane (1,2-DCA) via oxidative cleavage of a C-H bond (Pseudomonas sp. strain DCA1) versus C-Cl bond cleavage by SN2 reaction (Xanthobacter autotrophicus GJ10 and Ancylobacter aquaticus AD20). Compound-specific chlorine isotope analysis of 1,2-DCA was performed for the first time, and isotope fractionation (μbulk Cl) was determined by measurements of the same samples in three different laboratories using two gas chromatography-isotope ratio mass spectrometry systems and one gas chromatography-quadrupole mass spectrometry system. Strongly pathway-dependent slopes (Δδ13C/Δδ37Cl), 0.78 ± 0.03 (oxidation) and 7.7 ± 0.2 (SN2), delineate the potential of the dual isotope approach to identify 1,2-DCA degradation pathways in the field. In contrast to different μbulkC values [-3.5 ± 0.1‰ (oxidation) and -31.9 ± 0.7 and -32.0 ± 0.9‰ (SN2)], the obtained μbulkCl values were surprisingly similar for the two pathways: -3.8 ± 0.2‰ (oxidation) and -4.2 ± 0.1 and -4.4 ± 0.2‰ (SN2). Apparent kinetic isotope effects (AKIEs) of 1.0070 ± 0.0002 (13C-AKIE, oxidation), 1.068 ± 0.001 (13C-AKIE, SN2), and 1.0087 ± 0.0002 (37Cl-AKIE, SN2) fell within expected ranges. In contrast, an unexpectedly large secondary 37Cl-AKIE of 1.0038 ± 0.0002 reveals a hitherto unrecognized involvement of C-Cl bonds in microbial C-H bond oxidation. Our two-dimensional isotope fractionation patterns allow for the first time reliable 1,2-DCA degradation pathway identification in the field, which unlocks the full potential of isotope applications for this important groundwater contaminant.

Original languageEnglish
Pages (from-to)9430-9437
Number of pages8
JournalEnvironmental Science and Technology
Volume48
Issue number16
DOIs
StatePublished - 19 Aug 2014
Externally publishedYes

Fingerprint

Dive into the research topics of 'C and Cl isotope fractionation of 1,2-dichloroethane displays unique δ13C/δ37Cl Patterns for Pathway Identification and Reveals Surprising C-Cl bond involvement in microbial oxidation'. Together they form a unique fingerprint.

Cite this