Isotopic and Geochemical Analysis of Microbial Processes in Uncontaminated and Contaminated Ground Water and Sediment: Innovative Application of Radiocarbon

氯代烃（CHCs）在地下的生物降解是有问题的，因为这些化合物的顽固性和降解过程的复杂性。这项创新的实地研究的总体目标是利用放射性碳（14C）以及二氧化碳（CO2）和甲烷（CH4）的碳和氢稳定同位素（13C和氘（2H））来研究地下chc和自然存在的有机碳的原位微生物矿化。本研究将量化、比较和评价在不同氧化还原条件下，四氯乙烯（PCE）和三氯乙烯（TCE）在污染场地和未污染邻近地区的渗透带和地下水中的生物降解。PCE、TCE及其代谢物浓度和地球化学参数将使用标准技术（气相色谱法、分光光度法）进行测量。此外，将收集沉积物气相带CO2和CH4以及地下水溶解无机碳和CH4进行低温净化，利用加速器质谱（AMS）和质谱（MS）对14C和13C进行分析。将CO2和CH4的14C、13C和2H同位素监测与有限的污染物监测相结合，可以更好地区分未污染和受污染地下水中发生的生化过程。该技术区分了天然底物生物降解产生的CO2和CH4与CHC生物降解产生的CO2和CH4，可以在不同的低污染物和CO2和CH4浓度下使用。虽然放射性碳在环境生物降解研究中的应用相对较新，但它通常用于地质和考古年代测定。目前，微生物降解的间接证据和测量被用来估计自然存在的细菌对污染物去除的贡献。放射性碳测量将与稳定碳测量和代谢物监测结合使用，以改进对地下水中有机污染物的微生物降解的检测。虽然这项研究将研究用于干洗和工业应用的氯化溶剂的微生物降解，但这项技术应该适用于任何石油衍生的污染物，如多环芳烃（PAHs）、柴油和喷气燃料、取暖油和三硝基甲苯（TNT），因为这些化合物中的14C已经耗尽。该研究将扩大放射性碳作为环境示踪剂的应用范围，并为该技术在其他生化污染物研究中的应用奠定基础。该提案是为响应环境地球化学和生物地球化学招标NSF 99-9而提交的，由生物化学和生物化学研究所联合资助。

Aelion, MarjorieStone, PeterMCB-9975223AbstractQuantifying biodegradation of chlorinated hydrocarbons (CHCs) in the subsurface is problematic because of the recalcitrant nature of the compounds and the complexity of the degradation processes. The overall objective of this innovative field study is to investigate in situ microbial mineralization of CHCs and naturally-occurring organic carbon in the subsurface using radiocarbon (14C), and carbon and hydrogen stable isotopes (13C and deuterium (2H)) of carbon dioxide (CO2) and methane (CH4). This research will quantify, compare and evaluate tetrachloroethylene (PCE) and trichloroethylene (TCE) biodegradation in the vadose zone and groundwater from a contaminated field site and uncontaminated adjacent area, under varying redox conditions. PCE, TCE, concentrations of their metabolites, and geochemical parameters will be measured using standard techniques (gas chromatography, spectrophotometry). In addition, sediment vadose zone CO2 and CH4, and groundwater dissolved inorganic carbon and CH4 will be collected and purified cryogenically for 14C and 13C analysis by accelerator mass spectrometry (AMS) and mass spectrometry (MS). Combining isotopic monitoring of 14C, 13C and 2H of CO2 and CH4 with limited contaminant monitoring can better differentiate between biochemical processes occurring in uncontaminated and contaminted groundwater. This technique distinguishes between CO2 and CH4 produced from natural substrate biodegradation versus CHC biodegradation, and can be used under varying and low contaminant and CO2 and CH4 concentrations. Although the use of radiocarbon in environmental biodegradation studies is relatively new, it is used commonly in geological and archeological dating. Currently, indirect evidence and measurements of microbial degradation are used to estimate the contribution of naturally-occurring bacteria to contaminant removal. Radiocarbon measurements will be used in conjunction with stable carbon measurement and metabolite monitoring to improve the detection of microbial degradation of organic pollutants in groundwater. Although this research will examine microbial degradation of chlorinated solvents used in dry cleaning and industrial applications, this technique should apply to any petroleum-derived contaminant such as polycyclic aromatic hydrocarbons (PAHs), diesel and jet fuel, heating oil and trinitrotoluene (TNT), because 14C is depleted in these compounds. The proposed research will expand the use radiocarbon as an environmental tracer and lay the groundwork for the application of this technique to other biochemical contaminant studies.This proposal was submitted in response to the Environmental Geochemistry and Biogeochemistry solicitation NSF 99-9 and is being funded jointly by the Divisions of BIO and EAR.