Lay summary

Compound-specific isotope analysis is one of the key techniques for the identification of contaminant sources and assessment of formation and degradation processes of organic micropollutants. While conservative stable isotope ratios measured in individual compounds allow one to infer their precursor materials and (bio)synthesis pathways, stable isotope fractionation is indicative for the reaction mechanisms and extent of contaminant transformation. CSIA therefore contributes to a profound understanding of the reactive processes determining the fate of chemicals and thus to a proper assessment of the temporal and spatial variability of chemical pollution. Applications of CSIA have been particularly successful if isotope ratios were evaluated for two or more isotopic elements simultaneously. However, instrumental restrictions of the most widespread devices for CSIA, gas chromatography coupled to isotope ratio mass spectrometry (GC/IRMS), largely confine the use of CSIA to the elements C, N, H, and O as well as to compounds amenable to gas chromatography. As a consequence, more comprehensive applications that include more polar and ionic micropollutants and halogen isotopes are currently lacking.

With a multifunctional isotope ratio mass spectrometer, a team of environmental chemists and microbiologists will pursue new avenues for the coupling of liquid chromatography coupled to isotope ratio mass spectrometry (LC/IRMS) and for the analysis of chlorine isotope fractionation in volatile organic contaminants. The LC/IRMS option will be used for the isotopic analysis of polar organic micropollutants and their transformation products as well as for the exploration of isotope fractionation during oxidative transformations of pharmaceuticals and biocides. Chlorine isotope analysis with the dual-inlet IRMS option will enable us to generate reference materials for establishing new procedures of Cl isotope analysis by non-specialized benchtop quadrupol mass spectrometers. The latter will expand our abilities to carry out isotopic analyses beyond the capacity of the requested equipment. To this end, we will investigate the enzymatic mechanisms of isomer-specific hexachlorocyclohexane dechlorination pathways on the basis of C and Cl isotope fractionation analysis. The same isotopic elements will also enable us to use isotope effect as probes for precursor materials and mechanisms responsible for the formation of toxic chlorinated organic disinfection by-products during drinking water treatment.

With the requested instrumentation we will be able to make innovative contributions to emerging applications of CSIA. Moreover, our activities will provide a diverse group of researchers with access to stable-isotope based methods and help to establish new national and international collaborations.