Oxidation of fugitive methane in ground water linked to bacterial sulfate reduction
Oxidation of fugitive methane in ground water linked to bacterial sulfate reduction
复制标题
地下水中逃逸甲烷的氧化与细菌硫酸盐还原有关
作者：
D. V. Van Stempvoort;H. Maathuis;Ed Jaworski;B. Mayer;K. Rich
当逃逸性甲烷沿油气威尔斯井眼沿着向上运移时，它可能进入浅层地下水或通过上覆土壤进入大气。在这项研究之前，几乎没有关于迁移到地下水中的逃逸甲烷的命运的信息。在加拿大阿尔伯塔省阿尔伯塔省附近的一项野外研究中，我们发现水文地球化学证据表明，油井中的逃逸甲烷迁移到浅层含水层中，但在厌氧条件下，在低温（15 °C）下，异化细菌硫酸盐还原作用使甲烷衰减。证据包括地下水中甲烷和硫酸盐浓度的空间和时间趋势以及碳酸氢盐和硫化物浓度的相关趋势。在油井10 m范围内，硫酸盐浓度较低，硫酸盐在34S和18O中均富集。硫酸盐浓度与碳酸氢盐的δ 13 C值有很强的正相关性，与硫酸盐相比，硫化物在34S中被贫化。这些数据表明，细菌硫酸盐还原发生在生产井附近。在油井附近，观察到碳酸氢盐浓度升高，并且碳酸氢盐在13C中耗尽。建模表明，这种过量的13 C耗尽的碳酸氢盐的主要来源是氧化甲烷。与硫酸盐浓度和同位素数据相一致，这些结果支持了一种解释，即甲烷的原位细菌氧化与细菌硫酸盐还原有关。细菌硫酸盐还原可能在加拿大西部地下水中挥发性天然气的生物衰减中发挥重要作用。
When fugitive methane migrates upward along boreholes of oil and gas wells, it may migrate into shallow ground water or pass through overlying soil to the atmosphere. Prior to this study, there was little information on the fate of fugitive methane that migrates into ground water. In a field study near Lloydminster, Alberta, Canada, we found hydrogeochemical evidence that fugitive methane from an oil well migrated into a shallow aquifer but has been attenuated by dissimilatory bacterial sulfate reduction at low temperature (∼5°C) under anaerobic conditions. Evidence includes spatial and temporal trends in concentrations of methane and sulfate in ground water and associated trends in concentrations of bicarbonate and sulfide. Within 10 m of the oil well, sulfate concentrations were low, and sulfate was enriched in both 34S and 18O. Sulfate concentrations had a strong positive correlation with δ13C values of bicarbonate, and sulfide was depleted in 34S compared to sulfate. These data indicate that bacterial sulfate reduction occurred near the production well. Near the oil well, elevated concentrations of bicarbonate were observed, and the bicarbonate was depleted in 13C. Modeling indicates that the main source of this excess 13C‐depleted bicarbonate is oxidized methane. In concert with the sulfate concentration and isotope data, these results support an interpretation that in situ bacterial oxidation of methane has occurred, linked to bacterial sulfate reduction. Bacterial sulfate reduction may play a major role in bioattenuation of fugitive natural gas in ground water in western Canada.