2 research outputs found
Enantioselective Carbon Stable Isotope Fractionation of Hexachlorocyclohexane during Aerobic Biodegradation by <i>Sphingobium</i> spp.
Carbon
isotope fractionation was investigated for the biotransformation of
γ- and α- hexachlorocyclohexane (HCH) as well as enantiomers
of α-HCH using two aerobic bacterial strains: <i>Sphingobium
indicum</i> strain B90A and <i>Sphingobium japonicum</i> strain UT26. Carbon isotope enrichment factors (ε<sub>c</sub>) for γ-HCH (ε<sub>c</sub> = −1.5 ± 0.1‰
and −1.7 ± 0.2‰) and α-HCH (ε<sub>c</sub> = −1.0 ± 0.2‰ and −1.6 ± 0.3‰)
were similar for both aerobic strains, but lower in comparison with
previously reported values for anaerobic γ- and α-HCH
degradation. Isotope fractionation of α-HCH enantiomers was
higher for (+) α-HCH (ε<sub>c</sub> = −2.4 ±
0.8 ‰ and −3.3 ± 0.8 ‰) in comparison to
(−) α-HCH (ε<sub>c</sub> = −0.7 ± 0.2‰
and −1.0 ± 0.6‰). The microbial fractionation between
the α-HCH enantiomers was quantified by the Rayleigh equation
and enantiomeric fractionation factors (ε<sub>e</sub>) for <i>S. indicum</i> strain B90A and <i>S. japonicum</i> strain UT26 were −42 ± 16% and −22 ± 6%,
respectively. The extent and range of isomer and enantiomeric carbon
isotope fractionation of HCHs with <i>Sphingobium</i> spp.
suggests that aerobic biodegradation of HCHs can be monitored in situ
by compound-specific stable isotope analysis (CSIA) and enantiomer-specific
isotope analysis (ESIA). In addition, enantiomeric fractionation has
the potential as a complementary approach to CSIA and ESIA for assessing
the biodegradation of α-HCH at contaminated field sites
Carbon, Hydrogen and Chlorine Stable Isotope Fingerprinting for Forensic Investigations of Hexachlorocyclohexanes
Multielemental
stable isotope analysis of persistent organic pollutants
(POPs) has the potential to characterize sources, sinks, and degradation
processes in the environment. To verify the applicability of this
approach for source identification of hexachlorocyclohexane (HCHs),
we provide a data set of carbon, hydrogen, and chlorine stable isotope
ratios (δ<sup>13</sup>C, δ<sup>2</sup>H, δ<sup>37</sup>Cl) of its main stereoisomers (α-, β-, δ- and γ-HCHs)
from a sample collection based on worldwide manufacturing. This sample
collection comprises production stocks, agricultural and pharmaceutical
products, chemical waste dumps, and analytical-grade material, covering
the production time period from the late 1960s until now. Stable isotope
ratios of HCHs cover the ranges from −233‰ to +1‰,
from −35.9‰ to −22.7‰, and from −6.69‰
to +0.54‰ for δ<sup>2</sup>H, δ<sup>13</sup>C,
and δ<sup>37</sup>Cl values, respectively. Four groups of samples
with distinct multielemental stable isotope fingerprints were differentiated,
most probably as a result of purification and isolation processes.
No clear temporal trend in the isotope compositions of HCHs was found
at the global scale. The multielemental stable isotope fingerprints
facilitate the source identification of HCHs at the regional scale
and can be used to assess transformation processes. The data set and
methodology reported herein provide basic information for the assessment
of environmental field sites contaminated with HCHs