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Isotopic and Geochemical Assessment of in Situ Biodegradation of Chlorinated Hydrocarbons
Auteur(s)
Kirtland, Brian C.
Aelion, C. Marjorie
Stone, Peter A.
Date Issued
2003
Journal
Environmental Science & Technology, American Chemical Society (ACS), 2003/37/18/4205–4212
Abstract
Currently there is no in situ method to detect and quantify complete mineralization of chlorinated hydrocarbons (CHCs) to CO<sub>2</sub>. Combined isotopic measurements in conjunction with traditional chemical techniques were used to assess in situ biodegradation of trichloroethylene (TCE) and carbon tetrachloride (CT). Vadose zone CHC, ethene, ethane, methane, O<sub>2</sub>, and CO<sub>2</sub> concentrations were analyzed using gas chromatography over 114 days at the Savannah River Site. δ<sup>13</sup>C of CHC and δ<sup>13</sup>C and <sup>14</sup>C of vadose zone CO<sub>2</sub>, sediment organic matter, and groundwater dissolved inorganic carbon (DIC) were measured. Intermediate metabolites of TCE and CT accounted for ≤10% of total CHCs. δ<sup>13</sup>C of <i>cis</i>-1,2-dichloroethylene (DCE) was always heavier than TCE indicating substantial DCE biodegradation. <sup>14</sup>C-CO<sub>2</sub> values ranged from 84 to 128 percent modern carbon (pMC), suggesting that plant root-respired CO<sub>2</sub> was dominant. <sup>14</sup>C-CO<sub>2</sub> values decreased over time (up to 12 pMC), and contaminated groundwater <sup>14</sup>C-DIC (76 pMC) was substantially depleted relative to the control (121 pMC). <sup>14</sup>C provided a direct measure of complete CHC mineralization in vadose zone and groundwater in situ and may improve remediation strategies.
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Publication type
journal article
