Environmental Isotope Chemistry
Current Research Topics
Contamination of groundwater resources with chlorinated solvents, petroleum hydrocarbons and pesticides is widespread in both rural and urban settings and represents one of the most urgent challenges facing environmental science. Our group investigates the origin, transport and transformation of such contaminants by Compound Specific Isotope Analysis (CSIA). Stable isotope ratios are remarkably constant during physical distribution processes (dilution, sorption, etc.) whereas they are subject to pronounced isotope fractionation during (bio)transformation. Pronounced shifts in isotope ratios over time and distance in field studies can therefore be used as qualitative proof that degradation is occurring in the field or even to infer the extent of (bio)transformation.
While such isotope enrichment has long been regarded as “black box parameter”, we have recently developed a procedure that allows conversion to apparent kinetic isotope effects (AKIE) typical of certain transformation reactions. Degradation pathways may thus be identified from observable stable isotope fractionation, which is particularly important if products can be both, benign or more harmful than the parent compounds. (Elsner et al. 2005).
It is a major focus of our research group to pioneer such qualitative detection, pathway identification and quantification of (bio)degradation also for pesticides as a compound class for which CSIA has hardly been applied yet. This group of contaminants offers several challenges: Pesticides are water-soluble, little volatile and occur in relatively low concentrations in groundwater so that they are intrinsically difficult to analyze by CSIA. In addition, such agrochemicals are applied over greater areas so that modeling of transport and degradation becomes more difficult than in the case of single-source groundwater contaminations.
Goals of Our Research Group:
Development of enrichment and purification methods that allow Compound Specific Isotope Analysis (CSIA) for pesticides as a new class of important groundwater pollutants
Establish a new concept that deciphers degradation pathways from the observable isotope fractionation pattern of the respective (bio)transformation reaction in natural systems
Measure kinetic isotope effects as a mechanistic tool to elucidate the nature of the rate-limiting chemical step(s) in chemical and biological transformations
Use isotopic labels in organic contaminants to identify the contaminant degrading organisms (Collaboration with the group “Molecular Ecology”, T. Lüders, and “Anaerobic Degradation”, R. Meckenstock)
