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首页> 外文期刊>Journal of Geophysical Research. Biogeosciences >Assessment of microbial methane oxidation above a petroleum-contaminated aquifer using a combination of in situ techniques
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Assessment of microbial methane oxidation above a petroleum-contaminated aquifer using a combination of in situ techniques

机译：结合原位技术评估石油污染含水层上方的微生物甲烷氧化

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Emissions of the greenhouse gas CH4, which is often produced in contaminated aquifers, are reduced or eliminated by microbial CH4 oxidation in the overlying vadose zone. The aim of this field study was to estimate kinetic parameters and isotope fractionation factors for CH4 oxidation in situ in the vadose zone above a methanogenic aquifer in Studen, Switzerland, and to characterize the involved methanotrophic communities. To quantify kinetic parameters, several field tests, so-called gas push-pull tests (GPPTs), with CH4 injection concentrations ranging from 17 to 80 mL L1 were performed. An apparent V max of 0.70 ± 0.15 mmol CH4 (L soil air)1 h1 and an apparent K m of 0.28 ± 0.09 mmol CH4 (L soil air)1 was estimated for CH4 oxidation at 2.7 m depth, close to the groundwater table. At 1.1 m depth, K m (0.13 ± 0.02 mmol CH4 (L soil air)1) was in a similar range, but V max (0.076 ± 0.006 mmol CH4 (L soil air)1 h1) was an order of magnitude lower. At 2.7 m, apparent first-order rate constants determined from a CH4 gas profile (1.9 h1) and from a single GPPT (2.0 ± 0.03 h1) were in good agreement. Above the groundwater table, a V max much higher than the in situ CH4 oxidation rate prior to GPPTs indicated a high buffer capacity for CH4. At both depths, known methanotrophic species affiliated with Methylosarcina and Methylocystis were detected by cloning and sequencing. Apparent stable carbon isotope fractionation factors α for CH4 oxidation determined during GPPTs ranged from 1.006 to 1.032. Variability was likely due to differences in methanotrophic activity and CH4 availability leading to different degrees of mass transfer limitation. This complicates the use of stable isotopes as an independent quantification method.
机译：通常在受污染的含水层中产生的温室气体CH4的排放可通过上层渗流带中的微生物CH4氧化来减少或消除。这项现场研究的目的是估算瑞士Studen产甲烷层含水层上方渗流带中CH4原位氧化CH4的动力学参数和同位素分馏因子，并描述所涉及的甲烷营养族。为了量化动力学参数，已进行了几项现场试验，即所谓的气体推挽试验（GPPT），其中CH4的注入浓度为17至80 mL L1。估计在2.7 m深度处接近地下水位的CH4氧化的表观V max为0.70±0.15 mmol CH4（L土壤空气）1 h1，表观K m为0.28±0.09 mmol CH4（L土壤空气）1。在1.1 m深度处，K m（0.13±0.02 mmol CH4（L土壤空气）1 h）在相似的范围内，但V max（0.076±0.006 mmol CH4（L土壤空气）1 h1）低一个数量级。在2.7 m处，从CH4气体剖面（1.9 h1）和单个GPPT（2.0±0.03 h1）确定的表观一级速率常数非常吻合。在地下水位以上，V max远高于GPPT之前的原位CH4氧化速率，表明CH4具有很高的缓冲能力。在两个深度处，通过克隆和测序检测到与甲基骨孢菌和甲基囊藻相关的已知甲烷营养物种。 GPPT期间测定的CH4氧化的表观稳定碳同位素分馏因子α为1.006至1.032。变异性可​​能是由于甲烷营养活性和CH4利用率不同而导致的传质限制程度不同。这使稳定同位素作为独立的定量方法的使用变得复杂。

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