TY - JOUR
T1 - Cl and C isotope analysis to assess the effectiveness of chlorinated ethene degradation by zero-valent iron
T2 - Evidence from dual element and product isotope values
AU - Audí-Miró, Carme
AU - Cretnik, Stefan
AU - Otero, Neus
AU - Palau, Jordi
AU - Shouakar-Stash, Orfan
AU - Soler, Albert
AU - Elsner, Martin
N1 - Funding Information:
Audí-Miró, C. and Cretnik, S., contributed equally to this work. This study was funded by the Spanish Government CICYT projects CGL2008-06373-C03-01/03-BTE and CGL2011-29975-C04-01 and by the Catalan Government project 2009 SGR 103. The authors would like to thank the Valles Business Park enterprise for providing the zero valent iron, the Catalan Water Agency for their support and the “Institute of Groundwater Ecology” from the “Helmholtz Zentrum München” together with the “Centres Científics i Tecnològics” of the “Universitat de Barcelona” for the chemical analyses. A special thanks also to the reviewers of this work and to Tom Bullen for their helpful contributions.
PY - 2013/5
Y1 - 2013/5
N2 - This study investigated C and, for the first time, Cl isotope fractionation of trichloroethene (TCE) and cis-dichloroethene (cis-DCE) during reductive dechlorination by cast zero-valent iron (ZVI). Hydrogenolysis and β-dichloroelimination pathways occurred as parallel reactions, with ethene and ethane deriving from the β-dichloroelimination pathway. Carbon isotope fractionation of TCE and cis-DCE was consistent for different batches of Fe studied. Transformation of TCE and cis-DCE showed Cl isotopic enrichment factors (εCl) of -2.6‰±0.1‰ (TCE) and -6.2‰±0.8‰ (cis-DCE), with Apparent Kinetic Isotope Effects (AKIECl) for Cl of 1.008±0.001 (TCE) and 1.013±0.002 (cis-DCE). This indicates that a C-Cl bond breakage is rate-determining in TCE and cis-DCE transformation by ZVI. Two approaches were investigated to evaluate if isotope fractionation analysis can distinguish the effectiveness of transformation by ZVI as opposed to natural biodegradation. (i) Dual isotope plots. This study reports the first dual (C, Cl) element isotope plots for TCE and cis-DCE degradation by ZVI. The pattern for cis-DCE differs markedly from that reported for biodegradation of the same compound by KB-1, a commercially available Dehalococcoides-containing culture. The different trends suggest an expedient approach to distinguish abiotic and biotic transformation, but this needs to be confirmed in future studies. (ii) Product-related isotope fractionation. Carbon isotope ratios of the hydrogenolysis product cis-DCE differed consistently by 10‰ compared to the β-dichloroelimination products ethene and ethane providing a second line of evidence to differentiate abiotic or biotic degradation pathways.
AB - This study investigated C and, for the first time, Cl isotope fractionation of trichloroethene (TCE) and cis-dichloroethene (cis-DCE) during reductive dechlorination by cast zero-valent iron (ZVI). Hydrogenolysis and β-dichloroelimination pathways occurred as parallel reactions, with ethene and ethane deriving from the β-dichloroelimination pathway. Carbon isotope fractionation of TCE and cis-DCE was consistent for different batches of Fe studied. Transformation of TCE and cis-DCE showed Cl isotopic enrichment factors (εCl) of -2.6‰±0.1‰ (TCE) and -6.2‰±0.8‰ (cis-DCE), with Apparent Kinetic Isotope Effects (AKIECl) for Cl of 1.008±0.001 (TCE) and 1.013±0.002 (cis-DCE). This indicates that a C-Cl bond breakage is rate-determining in TCE and cis-DCE transformation by ZVI. Two approaches were investigated to evaluate if isotope fractionation analysis can distinguish the effectiveness of transformation by ZVI as opposed to natural biodegradation. (i) Dual isotope plots. This study reports the first dual (C, Cl) element isotope plots for TCE and cis-DCE degradation by ZVI. The pattern for cis-DCE differs markedly from that reported for biodegradation of the same compound by KB-1, a commercially available Dehalococcoides-containing culture. The different trends suggest an expedient approach to distinguish abiotic and biotic transformation, but this needs to be confirmed in future studies. (ii) Product-related isotope fractionation. Carbon isotope ratios of the hydrogenolysis product cis-DCE differed consistently by 10‰ compared to the β-dichloroelimination products ethene and ethane providing a second line of evidence to differentiate abiotic or biotic degradation pathways.
UR - http://www.scopus.com/inward/record.url?scp=84876322637&partnerID=8YFLogxK
U2 - 10.1016/j.apgeochem.2012.08.025
DO - 10.1016/j.apgeochem.2012.08.025
M3 - Article
AN - SCOPUS:84876322637
SN - 0883-2927
VL - 32
SP - 175
EP - 183
JO - Applied Geochemistry
JF - Applied Geochemistry
ER -