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Geochemical and Isotope Study of Trichloroethene Degradation in a Zero-Valent Iron Permeable Reactive Barrier: A Twenty-Two-Year Performance Evaluation
Wilkin, Richard T., Tony R. Lee, M. Sexton, Steven D. Acree, R. Puls, D. Blowes, C. Kalinowski, J. Tilton, AND L. Woods. Geochemical and Isotope Study of Trichloroethene Degradation in a Zero-Valent Iron Permeable Reactive Barrier: A Twenty-Two-Year Performance Evaluation. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 53:296-306, (2019). https://doi.org/10.1021/acs.est.8b04081
Volatile organic compounds are the most frequently encountered groundwater contaminants at hazardous waste sites. This study examines a twenty-two-year record of performance of a groundwater remediation technology used to treat volatile organic compounds, including trichloroethene, cis-dichloroethene, and vinyl chloride. These long-term performance data will help to improve system designs and guide the selection of remedial measures that best match site-specific hydrogeochemical conditions.
This study provides a twenty-two-year record of in situ degradation of chlorinated organic compounds by a granular iron permeable reactive barrier (PRB). Groundwater concentrations of trichloroethene (TCE) entering the PRB were as high as 10,670 µg/L. Treatment efficiency ranged from 81 to >99% and TCE concentrations ranged from C4 compounds, and possibly CO2(aq) and methane. Daughter products, cis-DCE and VC, represented <10% of influent TCE on a molar basis indicating low accumulation rates of undesired chlorinated products. The carbon isotope signal of TCE showed 13C-enrichment up to 18.7‰ within treated groundwater and an estimate of the bulk enrichment factor (ε) was -14‰. The δ13C values of methane within and down-gradient of the PRB varied widely from -94‰ to -16‰; these values cover most of the isotopic range encountered in natural methanogenic systems. The carbon isotope signatures of methane and inorganic carbon were consistent with open-system behavior and 22% molar conversion of CO2(aq) to methane.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL RISK MANAGEMENT RESEARCH LABORATORY
GROUNDWATER, WATERSHEDS, AND ECOSYSTEM RESTORATION DIVISION
SUBSURFACE PROCESSES AND PROTECTION BRANCH