Distinct Carbon Isotope Fractionation Signatures during Biotic and Abiotic Reductive Transformation of Chlordecone

摘要

Chlordecone is a synthetic organochlorine pesticide, extensively used in banana plantations of the French West Indies from 1972 to 1993. Due to its environmental persistence and bioaccumulation, it has dramatic public health and socio-economic impact. Here we describe a method for carbon-directed compound specific isotope analysis (CSIA) for chlordecone and apply it to monitor biotic and abiotic reductive transformation reactions, selected on the basis of their distinct product profiles (polychloroindenes versus lower chlorinated hydrochlordecones). Significant carbon isotopic enrichments were observed for all microbially mediated transformations (ε_(bulk) = −6.8‰ with a Citrobacter strain and ε_(bulk) = −4.6‰ with a bacterial consortium) and for two abiotic transformations (ε_(bulk) = −4.1‰ with zerovalent iron and ε_(bulk) = −2.6‰ with sodium sulfide and vitamin B_(12)). The reaction with titanium(III) citrate and vitamin B_(12), which shows the product profile most similar to that observed in biotic transformation, led to low carbon isotope enrichment (ε_(bulk) =−0.8‰). The CSIA protocol was also applied on representative chlordecone formulations previously used in the French West Indies, giving similar chlordecone δ~(13)C values from −31.1 ± 0.2‰ to −34.2 ± 0.2‰ for all studied samples. This allows the in situ application of CSIA for the assessment of chlordecone persistence.