Distinct carbon isotope fractionation during anaerobic degradation of dichlorobenzene isomers.
Chlorinated benzenes are ubiquitous organic contaminants found in groundwater and soils. Compound specific isotope analysis (CSIA) has been increasingly used to assess natural attenuation of chlorinated contaminants, in which anaerobic reductive dechlorination plays an essential role. In this work, carbon isotope fractionation of the three dichlorobenzene (DCB) isomers was investigated during anaerobic reductive dehalogenation in methanogenic laboratory microcosms. Large isotope fractionation of 1,3-DCB and 1,4-DCB was observed while only a small isotope effect occurred for 1,2-DCB. Bulk enrichment factors (εbulk) were determined from a Rayleigh model: -0.8 ± 0.1 ‰ for 1,2-DCB, -5.4 ± 0.4 ‰ for 1,3-DCB, and -6.3 ± 0.2 ‰ for 1,4-DCB. εbulk values were converted to apparent kinetic isotope effects for carbon (AKIE) in order to characterize the carbon isotope effect at the reactive positions for the DCB isomers. AKIE values are 1.005 ± 0.001, 1.034 ± 0.003, and 1.039 ± 0.001 for 1,2-DCB, 1,3-DCB, and 1,4-DCB, respectively. The large difference in AKIE values between 1,2-DCB and 1,3-DCB (or 1,4-DCB) suggests distinct reaction pathways may be involved for different DCB isomers during microbial reductive dechlorination by the methanogenic cultures.
Department of Earth Sciences, University of Toronto , Toronto, Ontario M5S 3B1, Canada.
Xiaoming
X
Liang
Scott O C
SO
Mundle
Jennifer L
JL
Nelson
Elodie
E
Passeport
Calvin C H
CC
Chan
Georges
G
Lacrampe-Couloume
Stephen H
SH
Zinder
Barbara
B
Sherwood Lollar
D000693:Anaerobiosis; D001673:Biodegradation, Environmental; D002247:Carbon Isotopes / Q000737:chemistry / Q000378:metabolism; D005591:Chemical Fractionation; D002722:Chlorobenzenes / Q000737:chemistry / Q000378:metabolism*; D007536:Isomerism; D007700:Kinetics
D002247:Carbon Isotopes; D002722:Chlorobenzenes; C004726:2-dichlorobenzene; C042146:1,3-dichlorobenzene; C018511:4-dichlorobenzene