1 research outputs found
Relative Contributions of <i>Dehalobacter</i> and Zerovalent Iron in the Degradation of Chlorinated Methanes
The
role of bacteria and zerovalent iron (Fe<sup>0</sup>) in the degradation
of
chlorinated solvents in subsurface environments is of interest to
researchers and remediation practitioners alike. Fe<sup>0</sup> used
in reactive iron barriers for groundwater remediation positively interacted
with enrichment cultures containing <i>Dehalobacter</i> strains
in the transformation of halogenated methanes. Chloroform transformation
and dichloromethane formation was up to 8-fold faster and 14 times
higher, respectively, when a <i>Dehalobacter</i>-containing
enrichment culture was combined with Fe<sup>0</sup> compared with
Fe<sup>0</sup> alone. The dichloromethane-fermenting culture transformed
dichloromethane up to three times faster with Fe<sup>0</sup> compared
to without. Compound-specific isotope analysis was employed to compare
abiotic and biotic chloroform and dichloromethane degradation. The
isotope enrichment factor for the abiotic chloroform/Fe<sup>0</sup> reaction was large at −29.4 ± 2.1‰, while that
for chloroform respiration by <i>Dehalobacter</i> was minimal
at −4.3 ± 0.45‰. The combined abiotic/biotic dechlorination
was −8.3 ± 0.7‰, confirming the predominance of
biotic dechlorination. The enrichment factor for dichloromethane fermentation
was −15.5 ± 1.5‰; however, in the presence of Fe<sup>0</sup> the factor increased to −23.5 ± 2.1‰,
suggesting multiple mechanisms were contributing to dichloromethane
degradation. Together the results show that chlorinated methane-metabolizing
organisms introduced into reactive iron barriers can have a significant
impact on trichloromethane and dichloromethane degradation and that
compound-specific isotope analysis can be employed to distinguish
between the biotic and abiotic reactions involved