HR: 1340h
AN: H33D-1627    [Abstracts]
TI: Reactive Transport Modelling of Heterocyclic Hydrocarbons at a Former Gasworks Site
AU: Herold, M
EM: maria.herold@geo.uni-goettingen.de
AF: University of Goettingen, Goldschmidtstrasse 3, Goettingen, D-37077, Germany
AU: * Ptak, T
EM: thomas.ptak@geo.uni-goettingen.de
AF: University of Goettingen, Goldschmidtstrasse 3, Goettingen, D-37077, Germany
AU: Wendel, T
EM: thomas.wendel@uni-tuebingen.de
AF: University of Tuebingen, Sigwartstrasse 10, Tuebingen, D-72076, Germany
AU: Grathwohl, P
EM: peter.grathwohl@uni-tuebingen.de
AF: University of Tuebingen, Sigwartstrasse 10, Tuebingen, D-72076, Germany
AB: Highly mobile heterocyclic hydrocarbons constitute a persistent threat to groundwater at a former gasworks site in Southern Germany. This area is currently being used as a test site for novel subsurface investigation techniques, as well as for a site-specific enhanced natural attenuation (ENA) remediation approach. The subsurface investigation consisted of direct-push borings and monitoring well installations, tracer tests, and Integral Pumping Tests (IPTs) at multiple control planes, which were positioned at different distances downgradient of the source zone and perpendicular to the contaminant plume transport direction. The numerical inversion of groundwater concentration time series measured during the IPTs, in combination with a groundwater flow and transport model of the test site, leads to estimations of total mass flow rates of contaminants or other groundwater parameters relevant to NA, as well as of average concentrations and concentration distributions along the control planes. Following detailed investigations of the microbial and chemical conditions at the site, an in-situ ENA method involving a circulation well and the use of O2 as a terminal electron acceptor was devised to aid aerobic microbial degradation of the heterocyclic compounds in the otherwise anoxic surroundings. The aims of the study presented here were to verify the proposed conceptual model of interacting physical and biogeochemical processes and to assess the effectiveness of the in-situ remediation approach with the help of multi-component reactive transport modelling, focusing on the situations (i) prior to the implementation of the in- situ remediation scheme and (ii) following the operation of the circulation well with O2 injection. A finite-difference model was devised using the software PMWIN and PHT3D, utilizing the collected data to simulate the relevant processes in two and three dimensions, respectively. Instead of using interpolated point scale concentration measurements, the results of the IPT evaluations were used as input for the reactive transport model, thereby making it more reliable due to the integrating nature of the IPT method.
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1828 Groundwater hydraulics
DE: 1831 Groundwater quality
DE: 1832 Groundwater transport
DE: 1847 Modeling
SC: Hydrology [H]
MN: 2007 Fall Meeting