1 Hydrogeology Department, Centre for Environmental Research UFZ Leipzig-Halle,
Permoserstrasse 15,D-04318 Germany

2 Groundwater Protection and Restoration Group, Department of Civil and Structural Engineering, University of Sheffield, Mappin Street, Sheffield S1 3JD, UK

Abstract The mass removal of an organic contaminant in an aquifer by microbial biodegradation has been the focus of a field case study of natural attenuation. By detailed numerical modelling we looked at the importance of field-scale Terminal Electron Accepting Processes (TEAP) based on results from previous laboratory experiments. A main aim was to study the dependence of results not only on parameter values, but also on the different concepts and approaches that the modelling was based upon. To be able to investigate this uncertainty in the results, we first had to build up the numerical and computational capability to perform a series of runs with models based on different approaches, including the most complex and thus demanding ones. Therefore, we applied parallel computing and automatic grid adaptation for a relatively comprehensive set of chemical species. Some of the conceptual changes had a large effect on the results; for example, the biodegradation concept. Some had only a minor influence, at least for this field site plume; for example, the permeability heterogeneities.

Keywords biodegradation concept; conceptual approach; groundwater; natural attenuation; numerical simulation; parameter sensitivity; three-dimensional