Stimulated reductive dechlorination identified with induced polarization - a new opportunity to monitor in situ remediation of chlorinated solvents?

Theme; 1. Dealing with contamination of soil, groundwater and sedimentDevelopments in technologies, policies, concepts, regulation, managementTitle of session; 1a. Assessment and monitoringSubject: New investigation and monitoring techniques Titel: ”Stimulated reductive dechlorination identified with induced polarization - a new opportunity to monitor in situ remediation of chlorinated solvents?”Presenter and authors: Charlotte Sparrenbom1, Sofia Åkesson1, David Hagerberg1 & 2, Sara Johansson2 & 3, Torleif Dahlin31.Department of Geology, Lund University, Lund, Sölvegatan 12, SE-223 62 Lund, SwedenTel: +46462223954, mob: +46 72 2225266E-mail: charlotte.sparrenbom@geol.lu.se 2.Tyréns AB, Isbergs gata 15, SE-205 19 Malmö, Sweden3.Engineering Geology, Lund University, Box 118, SE-221 00 Lund, SwedenPoster presentationPresently in Sweden, large numbers of polluted areas are remediated by excavation and then deposition of contaminated masses on landfills or in best cases off site treatment efforts. In-situ remediation and especially the monitoring thereof needs further development to avoid the costly and somewhat hazardous shipments associated with excavation. The monitoring of in-situ remediation actions needs easier and cheaper nondestructive methods for evaluation of remediation degree and degradation status of the contaminant. Within the TRansparent Underground Structures research project (TRUST), we investigate the Direct Current resistivity and time-domain Induced Polarization tomography (DCIP) method and its use within the context of DNAPL contaminated sites. DCIP is an emerging and promising new technique for 2D, 3D and 4D mapping of underground hydrogeochemical structures and details, as well as spatial distribution of contaminants. DCIP is a non-invasive and non-destructive geoelectrical measurement method that among other things has high potential for providing indirect evidence of contaminant degradation status. In our investigations, we show the results from DCIP measurements in an area where pilot studies with stimulated reductive dechlorination have been performed on an old industrial (textile and mechanical industry) site highly contaminated with TCE and its degradation products. The area treated reveal sharp anomalies in the DCIP response and more ongoing measurements and groundwater sampling is currently taking place to study and evaluate the possible uses, benefits and limitations of the technique. Other promising uses for the DCIP technique are to monitor changes and to delimit areas polluted by chlorinated solvents (DNAPL).Our current investigations focus on the soil and groundwater geochemistry and its DCIP response patterns and causes, as well as its possible temporal changes due to geochemical changes when pollutant degradation occur and concentration changes. Several drillings together with soil and groundwater samplings provide reference data showing free-phase TCE in part of the soil and a complex geological setting with quick transport pathways within the fissured bedrock aquifer below the top soil cover. We aim to establish if differences in IP effects and changes in IP anomalies can become a future effective tool for evaluating the degree of degradation and monitor in-situ remediation of chlorinated hydrocarbons as well as to delimit the areas affected by the pollutant