A Stable Isotope Perspective on (Bio)degradation of Organic Contaminants
Compound-speciﬁc stable isotope analysis (CSIA) oﬀers unique avenues to study transformation processes of organic contaminants in natural and engineered environments. Thanks to systematic investigations of isotope eﬀects associated with the enzyme-catalyzed, abiotic, and photochemical reactions of organic compounds, it is now possible to infer pathways and extents of degradation of many priority contaminants from changes of their stable isotope ratios. This so-called isotope fractionation is independent of the time-scales over which the observed processes occur, thus making CSIA complementary to the suite of analytical, biological, computational tools for the assessment of contaminant degradation. In addition to supporting the evaluation of pollutant exposure to humans and the environment, stableisotope-based studies also enable rigorous analyses of reaction kinetics that allow for novel and fundamental insights into the mechanisms of enzyme- and mineral-catalyzed processes. In this virtual seminar, I will elaborate on both of these aspects of CSIA. I will ﬁrst illustrate the utility of 13C/12C and 15N/14N ratio analyses for evaluating the fate of pesticides in soil, namely for assessing the concurrent formation, degradation, and transport of desphenylchloridazon, a persistent metabolite of the herbicide chloridazon and frequently detected groundwater contaminant. The second part will be dedicated to contaminant-degrading non-heme iron oxygenases and how isotopic analyses reveals their catalytic cycle and the remarkably low eﬃciency of these enzymes towards oxidative contaminant biodegradation.
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