Title of article :
Assessing in situ mineralization of recalcitrant organic compounds in vadose zone sediments using δ13C and 14C measurements
Author/Authors :
Brian C. Kirtland، نويسنده , , C. Marjorie Aelion، نويسنده , , Peter A. Stone، نويسنده ,
Issue Information :
روزنامه با شماره پیاپی سال 2005
Pages :
18
From page :
1
To page :
18
Abstract :
Few techniques exist to measure the biodegradation of recalcitrant organic compounds such as chlorinated hydrocarbons (CHC) in situ, yet predictions of biodegradation rates are needed for assessing monitored natural attenuation. Traditional techniques measuring O2, CO2, or chemical concentrations (in situ respiration, metabolite and soil air monitoring) may not be sufficiently sensitive to estimate biodegradation rates for these compounds. This study combined isotopic measurements (14C and δ13C of CO2 and δ13C of CHCs) in conjunction with traditional methods to assess in situ biodegradation of perchloroethylene (PCE) and its metabolites in PCE-contaminated vadose zone sediments. CHC, ethene, ethane, methane, O2, and CO2 concentrations were measured over 56 days using gas chromatography (GC). δ13C of PCE, trichloroethylene (TCE) and cis-1,2-dichloroethylene (DCE), δ13C and 14C of vadose zone CO2 and sediment organic matter, and δ13C, 14C, and δD of methane were measured using a GC-isotope ratio mass spectrometer or accelerator mass spectrometer. PCE metabolites accounted for 0.2% to 18% of CHC concentration suggesting limited reductive dechlorination. Metabolites TCE and DCE were significantly enriched in 13C with respect to PCE indicating metabolite biodegradation. Average δ13C-CO2 in source area wells (−23.5‰) was significantly lower compared to background wells (−18.4‰) indicating CHC mineralization. Calculated CHC mineralization rates were 0.003 to 0.01 mg DCE/kg soil/day based on lower 14C values of CO2 in the contaminated wells (63% to 107% modern carbon (pMC)) relative to the control well (117 pMC). Approximately 74% of the methane was calculated to be derived from in situ CHC biodegradation based on the 14C measurement of methane (29 pMC). 14C-CO2 analyses was a sensitive measurement for quantifying in situ recalcitrant organic compound mineralization in vadose zone sediments for which limited methodological tools exist.
Keywords :
biodegradation , radiocarbon , Monitored natural attenuation , stable isotopes , PCE , Bioremediation
Journal title :
Journal of Contaminant Hydrology
Serial Year :
2005
Journal title :
Journal of Contaminant Hydrology
Record number :
693599
Link To Document :
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