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McKelvey School of Engineering

EECE Seminar ~ Dr. Thomas Hofstetter

Friday, November 6 | 11:00 AM - 12:00 PM

Virtual Event

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.


Event Type



McKelvey School of Engineering


Science & Technology



Energy, Environmental & Chemical Engineering


Event Contact

Patty Kofron, pkofron@wustl.edu

Speaker Information

Thomas B. Hofstetter is a Senior Scientist at the department of Environmental Chemistry at the Swiss Federal Institute of Aquatic Science and Technology(Eawag)andaLecturerinEnvironmentalChemistryattheSwiss Federal Institute of Technology ETH Zürich. Dr. Hofstetter obtained his PhD in Environmental Sciences from ETH Zürich in 1999 under the guidance of Rene Schwarzenbach. After working three years on the life cycle assessment of chemicals in collaboration with the Chemical Industry, his returntotheworldoforganicwatercontaminantsledhimbacktoETHZürich, where we also obtained his habilitation (Venia Legedi) in 2008, and, as guest investigator to the Woods Hole Oceanographic Institution in 2005 and the University of Minnesota in 2012. Thomas Hofstetter joined Eawag in 2010 where he studies enzyme mechanisms and isotope effects of organic contaminant transformation, stable-isotope based methods to track such reactions in aquatic and soil environments, as well as the redox properties of ironbearing minerals. He became associate editor for Environmental Science & Technology in 2016.

[Host:  Dr. Kimberly Parker]

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