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Dresden, Germany

Schubert M.,Helmholtz Center for Environmental Research | Schmidt A.,Helmholtz Center for Environmental Research | Muller K.,GICON GmbH | Weiss H.,Helmholtz Center for Environmental Research
Journal of Environmental Radioactivity | Year: 2011

A common approach for remediation of groundwater contamination with volatile organic compounds (VOCs) is contaminant stripping by means of in situ air sparging (IAS). For VOC stripping, pressurized air is injected into the contaminated groundwater volume, followed by the extraction of the contaminant-loaded exhaust gas from the vadose soil zone and its immediate on-site treatment. Progress assessment of such remediation measure necessitates information (i) on the spatial range of the IAS influence and (ii) on temporal variations of the IAS efficiency. In the present study it was shown that the naturally occurring noble gas radon can be used as suitable environmental tracer for achieving the related spatial and temporal information. Due to the distinct water/air partitioning behaviour of radon and due to its straightforward on-site detectability, the radon distribution pattern in the groundwater can be used as appropriate measure for assessing the progression of an IAS measure as a function of space and time. The presented paper discusses both the theoretical background of the approach and the results of an IAS treatment accomplished at a VOC contaminated site lasting six months, during which radon was applied as efficiency indicator. © 2010 Elsevier Ltd. Source

Lamert H.,Helmholtz Center for Environmental Research | Geistlinger H.,Helmholtz Center for Environmental Research | Werban U.,Helmholtz Center for Environmental Research | Schutze C.,Helmholtz Center for Environmental Research | And 10 more authors.
Environmental Earth Sciences | Year: 2012

Potential pathways in the subsurface may allow upwardly migrating gaseous CO 2 from deep geological storage formations to be released into near surface aquifers. Consequently, the availability of adequate methods for monitoring potential CO 2 releases in both deep geological formations and the shallow subsurface is a prerequisite for the deployment of Carbon Capture and Storage technology. Geoelectrical surveys are carried out for monitoring a small-scale and temporally limited CO 2 injection experiment in a pristine shallow aquifer system. Additionally, the feasibility of multiphase modeling was tested in order to describe both complex non-linear multiphase flow processes and the electrical behavior of partially saturated heterogeneous porous media. The suitability of geoelectrical methods for monitoring injected CO 2 and geochemically altered groundwater was proven. At the test site, geoelectrical measurements reveal significant variations in electrical conductivity in the order of 15-30 %. However, site-specific conditions (e. g., geological settings, groundwater composition) significantly influence variations in subsurface electrical conductivity and consequently, the feasibility of geoelectrical monitoring. The monitoring results provided initial information concerning gaseous CO 2 migration and accumulation processes. Geoelectrical monitoring, in combination with multiphase modeling, was identified as a useful tool for understanding gas phase migration and mass transfer processes that occur due to CO 2 intrusions in shallow aquifer systems. © 2012 Springer-Verlag. Source

Peter A.,University of Kiel | Lamert H.,Helmholtz Center for Environmental Research | Beyer M.,GICON GmbH | Hornbruch G.,University of Kiel | And 11 more authors.
Environmental Earth Sciences | Year: 2012

A small scale and temporally limited CO 2 injection test was performed in a shallow aquifer to investigate the geochemical impact of CO 2 upon such aquifers and to apply and verify different monitoring methods. Detailed site investigation coupled with multiphase simulations were necessary to design the injection experiment and to set up the monitoring network, before CO 2 was injected over a ten-day period at three injection wells, at a depth of 18 m below surface level into a quaternary sand aquifer located close to the town of Wittstock in Northeast Germany. Monitoring methods comprised groundwater sampling and standard analyses, as well as trace element analyses and isotope analyses; geoelectrical borehole monitoring; passive samplers to analyse temporally integrated for cations and multi-parameter probes that can measure continuously for dissolved CO 2, pH and electrical conductivity. Due to CO 2 injection, total inorganic carbon concentrations increased and pH decreased down to a level of 5. 1. Associated reactions comprised the release of major cations and trace elements. Geoelectrical monitoring, as well as isotope analyses and multi-parameter probes proved to be suitable methods for monitoring injected CO 2 and/or the alteration of groundwater. © 2012 Springer-Verlag. Source

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