Spatial & Temporal Dynamics in a Tar Oil Contaminated Aquifer: Focus on Microbial Activities

When organic compounds, e.g. toluene or naphthalene, reach the soil and groundwater, contamination plumes with steep characteristic redox gradients are built. With a regularly conducted vertically high resolved analysis of groundwater as well as of sediment samples at a site in Düsseldorf over 4 years, dynamics of the vertical expansion of the contaminant plume and the maximal contaminant concentrations could be revealed, although when only small fluctuations of the groundwater table took place. Even within a very short time span (2 weeks), small changes in the contaminant distribution with accompanied sulfide occurrence, a degradation product, could be detected, that shows an unexpected fast adaption possibility of the microorganisms. However, 2008 a collapse of toluene biodegradation was observed, supporting the assumption that dynamics inhibiting the microbial degradation rather than enhancing as soon as they are stronger.