Compound specific isotope analysis of hexachlorocyclohexane isomers: a method for source fingerprinting and field investigation of in situ biodegradation

Abstract

A method was successfully developed for the CSIA of HCH isomers that showed potential for HCH source differentiation and identification of HCH in situ biodegradation. At the HCH-contaminated site, the observed preferential isotopic enrichment of certain isomers relative to others for a given source allows differentiation between biodegraded and non-biodegraded HCH.

Assessment of 2,4-Dinitroanisole Transformation Using Compound-Specific Isotope Analysis after In Situ Chemical Reduction of Iron Oxides

“…One major challenge when applying an in situ (bio)­remediation technique is providing a reliable evaluation of performance; it is difficult to quantify the amount of transformed contaminants from concentration measurements alone. − For example, the need to (repeatedly) inject aqueous solutions containing electron donors into the subsurface introduces perturbations that may lead to pollutant dilution without degradation. Moreover, reduction of Fe­(III) induces partial reductive dissolution and transformation of reactive Fe minerals and could mobilize solid-bound contaminants. ,− …”

Compound-Specific Stable Isotope Analysis: Implications in Hexachlorocyclohexane in-vitro and Field Assessment

“…Amidst these contaminants, HCH isomers are often the most disregarded ones with a very few reports on carbon and chlorine isotope fractionation supplemented with only a limited data [19,[57][58][59][60][61]. Because of their high persistence, toxicity and unusual process of production which have generated large amounts of waste, HCH isomers stand out to be ideal for studying insights into their potential management.…”

“…The mere decrease in concentration of the contaminant in the environment does not reflect the sole ability of applied remediation measure rather it leaves behind an important virtue of natural attenuation unattended. So far, initially a method was successfully developed for the CSIA of HCH isomers which showed potential for HCH source differentiation and identification in the groundwater of an operating packaging and reformulating pesticide facility located in northeastern Florida, USA [61]. Recently, in a study performed by Bashir et al (2015) the efficacy of CSIA was tested for determining carbon stable isotope ratios of HCH isomers directly from contaminated aquifer located in the vicinity of the former formulation and packing plant located in Germany.…”

“…However, in complex environmental conditions, the isotope fractionation can be affect by many different factors and may remain masked or hidden during the analysis and in such cases, dual-element stable isotope analysis provides an elegant way to improve the quantification using CSIA. Since a dual-element isotope analysis is less affected by masking of isotope effects or methodological differences [61].…”

Assessment of 2,4-Dinitroanisole Transformation Using Compound-Specific Isotope Analysis After in Situ Chemical Reduction of Iron Oxides

“…14,19,20 One major challenge when applying an in situ (bio)remediation technique is providing a reliable evaluation of performance; it is difficult to quantify the amount of transformed contaminants from concentration measurements alone. [21][22][23] For example, the need to (repeatedly) inject aqueous solutions containing electron donors into the subsurface introduces perturbations that may lead to pollutant dilution without degradation. Moreover, reduction of Fe(III) induces partial reductive dissolution and transformation of reactive Fe minerals and could mobilize solid-bound contaminants.…”