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

Aelion，MarjorieStone，PeterMCB-9975223摘要由于氯代烃（CHCs）的难降解性和降解过程的复杂性，因此定量地下CHCs的生物降解是有问题的。 这项创新性实地研究的总体目标是使用放射性碳（14 C）以及二氧化碳（CO2）和甲烷（CH 4）的碳和氢稳定同位素（13 C和氘（2 H）），调查地下CHCs和天然有机碳的原位微生物矿化。 本研究将量化，比较和评估四氯乙烯（PCE）和三氯乙烯（TCE）的生物降解包气带和地下水从污染的现场和未污染的邻近地区，在不同的氧化还原条件下。 将使用标准技术（气相色谱法、分光光度法）测量PCE、TCE及其代谢物的浓度和地球化学参数。 此外，沉积物包气带CO2和CH 4，以及地下水溶解的无机碳和CH 4将被收集和低温净化，用于加速器质谱（AMS）和质谱（MS）的14 C和13 C分析。 将CO2和CH 4的14 C、13 C和2 H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污染地下水中发生的生物化学过程。 该技术区分了天然基质生物降解与CHC生物降解产生的CO2和CH 4，并可在不同和低污染物以及CO2和CH 4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定年。目前，微生物降解的间接证据和测量用于估计自然发生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微生物降解的检测。 虽然这项研究将检查用于干洗和工业应用的氯化溶剂的微生物降解，但这项技术应适用于任何石油衍生的污染物，如多环芳烃（PAH），柴油和喷气燃料，取暖油和三硝基甲苯（TNT），因为14 C在这些化合物中耗尽。 这项研究将扩大放射性碳作为环境示踪剂的应用范围，并为将这项技术应用于其他生物化学污染物的研究奠定基础。这项研究是应NSF 99-9环境地球化学和生物地球化学征集的要求提交的，目前由BIO和NPO部门共同资助。

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.