Sandra Dworatzek and Jennifer Webb, (Ontario) coauthored a paper entitled “Transformation of Chlorofluorocarbons Investigated via Stable Carbon Compound-Specific Isotope Analysis” that was published in Environmental Science & Technology, currently an ASAP article, first published online December 2, 2019.

Elizabeth Phillips (Department of Earth Sciences, University of Toronto) was the lead author and her coauthors in addition to Sandra and Jennifer included Tetyana Gilevska, Axel Horst, Jesse Manna and Barbara Sherwood Lollar from the University of Toronto, Edward Seger and Edward J. Lutz from the Chemours Company, Scott Norcross, Scott A. Morgan and Kathryn A. West from AECOM and E. Erin Mack from DuPont de Nemours and Company.

Sandra is a Principal at SiREM, with more than 17 years of experience focused on oversight of laboratory treatability studies and the development and scaleup of new bioaugmentation cultures.

Jennifer is the Research Coordinator at SiREM with more than 16 years of experience in microbiology where she develops new cultures while coordinating R&D collaborations with researchers globally.

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Compound-specific isotope analysis (CSIA) is a valuable tool in contaminant remediation studies. Chlorofluorocarbons (CFCs) are ozone-depleting substances previously thought to be persistent in groundwater under most geochemical conditions but more recently have been found to (bio)transform in some laboratory experiments. To date, limited applications of CSIA to CFCs have been undertaken. Here, biotransformation-associated carbon isotope enrichment factors, εC,bulk for CFC-113 (εC,bulk = −8.5 ± 0.4‰) and CFC-11 (εC,bulk = −14.5 ± 1.9‰), were determined. δ13C signatures of pure-phase CFCs and hydrochlorofluorocarbons were measured to establish source signatures. These findings were applied to investigate potential in situ CFC transformation in groundwater at a field site, where carbon isotope fractionation of CFC-11 suggests naturally occurring biotransformation by indigenous microorganisms. The maximum extent of CFC-11 transformation is estimated to be up to 86% by an approximate calculation using the Rayleigh concept. CFC-113 δ13C values in contrast were not resolvably different from pure-phase sources measured to date, demonstrating that CSIA can aid in identifying which compounds may, or may not, be undergoing reactive processes at field sites. Science and public attention remains focused on CFCs, as unexplained source inputs to the atmosphere have been recently reported, and the potential for CFC biotransformation in surface and groundwaters remains unclear. This study proposes δ13C CSIA as a novel application to study the fate of CFCs in groundwater.

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