HR: 0830h
AN: H11D-0884    [PDF]
TI: High Resolution Multi-Level Monitoring and Characterization of NA Processes
AU: Piepenbrink, M
EM: matthias.piepenbrink@uni-tuebingen.de
AF: University of Tuebingen, Center for Applied Geoscience, Sigwartstrasse 10, Tuebingen, D-72076 Germany
AU: * Ptak, T
EM: thomas.ptak@uni-tuebingen.de
AF: University of Tuebingen, Center for Applied Geoscience, Sigwartstrasse 10, Tuebingen, D-72076 Germany
AU: Grathwohl, P
EM: peter.grathwohl@uni-tuebingen.de
AF: University of Tuebingen, Center for Applied Geoscience, Sigwartstrasse 10, Tuebingen, D-72076 Germany
AB: Monitored natural attenuation is a potentially valuable risk-based remediation strategy for contaminated groundwater. The most important mass-removal process for natural attenuation is biodegradation. Certain zones or fringes of a contaminant plume offer enhanced conditions for biodegradation: microbes, nutrients, contaminants and electron donors / acceptors are not only found together but also in the required reaction ratios. Due to this fact these areas show a relative rapid degradation and provide a significant contribution to the overall reduction of mass within the plume. As can be shown by high resolution numerical simulations of reactive transport in groundwater, the spatial distribution of these highly reactive zones, compared to the volume of the whole plume, is quite small and characterized by steep concentration gradients, which can not be detected using standard monitoring procedures. High resolution multi-level sampling (MLS) in the order of 0.1m or less is an essential prerequisite for the investigation of NA processes within the reactive fringes at field scale. This contribution presents results from ongoing research on high resolution MLS at six field sites in different European countries. The focus was on an optimized site-specific hydraulic design and contaminant - MLS-material interaction. Most acceptable solutions (which means MLS resolution in the order of 0.1m) were found using sampling tubes with a small inner diameter (3-4mm). This results in a small stagnant water volume prior to sampling, but is still not problematic with respect to the flow induced hydraulic losses within the tube. Another requirement for high resolution sampling was to abandon standard sampling protocols (DIN, EPA, .) which often demand huge groundwater volumes (1 liter) for every single compound to be analyzed. To estimate the effects of the tubing material on the quality of the groundwater samples, an analytical model by Reynolds et al. (1990) was used to study the sorptive uptake of different organics by different tubing polymers, considering partitioning coefficients, intra-polymeric diffusion coefficients and tube-surface to tube-volume ratios.
DE: 0400 Biogeosciences
DE: 1800 HYDROLOGY
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1894 Instruments and techniques
SC: Hydrology [H]
MN: 2003 Fall Meeting