Hydrogen Isotope Fractionation during the Biodegradation of 1,2-Dichloroethane: Potential for Pathway Identification Using a Multi-element (C, CI, and H) Isotope Approach

作者：Palau Jordi^*; Shouakar Stash Orfan; Mortan Siti Hatijah; Yu Rong; Rosell Monica; Marco Urrea Ernest; Freedman David L; Aravena Ramon; Soler Albert; Hunkeler Daniel

来源：Environmental Science & Technology, 2017, 51(18): 10526-10535.

DOI：10.1021/acs.est.7b02906

Even though multi-element isotope fractionation patterns provide crucial information with which to identify contaminant degradation pathways in the field, those involving hydrogen are still lacking for many halogenated groundwater contaminants and degradation pathways. This study investigates for the first time hydrogen isotope fractionation during both aerobic and anaerobic biodegradation of 1,2-dichloroethane (1,2-DCA) using five microbial cultures. Transformation-associated isotope fractionation values (epsilon(H)(bulk)) were -115 +/- 18% (aerobic C-H bond oxidation), -34 +/- 4 parts per thousand and -38 +/- 4 parts per thousand (aerobic C-Cl bond cleavage via hydrolytic dehalogenation), and -57 +/- 3 parts per thousand and -77 +/- 9 parts per thousand (anaerobic C-Cl bond cleavage via reductive dihaloelimination). The dual-element C-H isotope approach (Delta(C-H) = Delta delta H-2/Delta delta C-13 approximate to epsilon(H)(bulk)/epsilon(C)(bulk), where Delta delta H-2 and Delta delta C-13 are changes in isotope ratios during degradation) resulted in clearly different Lambda(C-H) values: 28 +/- 4 (oxidation), 0.7 +/- 0.1 and 0.9 +/- 0.1 (hydrolytic dehalogenation), and 1.76 +/- 0.05 and 3.5 +/- 0.1 (dihaloelimination). This result highlights the potential of this approach to identify 1,2-DCA degradation pathways in the field. In addition, distinct trends were also observed in a multi- (i.e.,Delta delta H-2 versus Delta delta Cl-37 versus Delta delta C-13) isotope plot, which opens further possibilities for pathway identification in future field studies. This is crucial information to understand the mechanisms controlling natural attenuation of 1,2-DCA and to design appropriate strategies to enhance biodegradation.

• 出版日期2017-9-19