Critical Zone Hydrology Group

Model-assisted interpretation of CSIA data in polluted aquifers

Supervisors and collaborators:

• B.M. van Breukelen - VU University
• Tomasz Kuder - the University of Oklahoma
• Ivonne Nijenhuis - Helmholtz Centre of Environmental Research - UFZ

Duration: 2012-2015
Funding: 7th Framework Programme of the European Union (project: CSI: ENVIRONMENT).

Project description

Compound-specific stable isotope analysis (CSIA) has proven in the last decade as a valuable method to quantify the extent of degradation of various key organic pollutants (chlorinated ethenes, BTEX, MTBE) at contaminated sites. During degradation, heavy isotopologues are transformed with slightly lower rate constants than the abundant light isotopologues, causing a (heavy to light) isotope enrichment in the pollutant and a depletion in the reaction product. The extent of transformation follows from the change in isotope ratio and the kinetic isotope fractionation factor for the process. CSIA data, therefore, give direct information on transformation processes, whereas concentration decreases can be solely due to dilution. As degradation-induced isotope signals are somewhat modified by physical processes (hydrodynamic dispersion, sorption) and as degradation may occur via complex reaction networks (sequential reductive dechlorination of chlorinated ethenes) we employ reactive transport modeling to simulate simultaneously pollutant concentrations and their isotope ratios to aid in the interpretation of CSIA data at contaminated sites.
In this project we will continue the development of these RTMs with focus on chlorinated ethenes and multidimensional CSIA (C, H, Cl). We will apply the model to simulate laboratory experiments and field site data.