High-resolution magnetic susceptibility measurements for investigating magnetic mineral formation during microbial mediated iron reduction
High-resolution magnetic susceptibility measurements for investigating magnetic mineral formation during microbial mediated iron reduction
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DOI：
10.1002/2013jg002414
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发表时间：
2014-01-01
影响因子：
3.7
通讯作者：
Slater, Lee D.
中科院分区：
文献类型：
--
作者：
Atekwana, Estella A.;Mewafy, Farag M.;Slater, Lee D.
同化铁还原菌在铁(氢)氧化物还原和产生具有磁性的二次固体铁矿物相过程中起着重要作用。因此，磁化率可以在确定微生物介导的铁还原发生的区域中发挥重要作用。我们研究了一个受碳氢化合物污染的含水层的磁化率变化，其中甲烷生成和铁还原是主要的生物地球化学过程。我们的目标是(1)确定磁化率的可变性，(2)确定对磁化率可变性的水生物地球化学控制，以及(3)评估磁化率作为识别发生铁和有机碳循环耦合的区域的可行技术的使用。磁化率数据是在污染和未污染地区的11个钻孔中获得的。结果表明，自由相羽流中钻孔的磁化率值高于溶解相羽流和背景中的钻孔磁化率。磁化率值在地下水位波动带内最高，峰值主要出现在最高水位线上，并与高浓度的溶解Fe(II)和有机碳含量相吻合，表明地下水位波动带具有最强的生物活动性。在游离相羽流上方的包气带内的高磁化率值与甲烷枯竭区相吻合，表明甲烷与铁还原耦合的好氧或厌氧氧化作用。结果表明，磁化率可作为铁碳循环研究的一种可行工具。微生物介导的铁还原可导致磁铁矿的析出，磁化率较高的磁化率出现在铁还原带内。磁化率在铁碳循环研究中是一个可行的工具
Disimilatory iron-reducing bacteria play an important role in the reduction of Fe(hydr)oxides and the production of secondary solid-iron mineral phases that can have magnetic properties. Magnetic susceptibility can therefore play an important role in identifying zones where microbial-mediated iron reduction is occurring. We investigated the magnetic susceptibility variations in a hydrocarbon-contaminated aquifer where methanogenesis and iron reduction are the main biogeochemical processes. Our objectives are to (1) determine the variability of magnetic susceptibility, (2) determine the hydrobiogeochemical controls on the magnetic susceptibility variability, and (3) evaluate the use of magnetic susceptibility as a viable technique for identifying zones where the coupling of iron and organic carbon cycling is occurring. Magnetic susceptibility data were acquired down 11 boreholes within contaminated and uncontaminated locations. We show that magnetic susceptibility values for boreholes within the free phase plume are higher than values for boreholes within the dissolved phase plume and background. Magnetic susceptibility values are highest within the zone of water table fluctuation with peaks predominantly occurring at the highest water table marks and are also coincident with high concentrations of dissolved Fe(II) and organic carbon content, suggesting that the zone of water table fluctuation is most biologically active. High magnetic susceptibility values within the vadose zone above the free phase plume are coincident with a zone of methane depletion suggesting aerobic or anaerobic oxidation of methane coupled to iron reduction. Our results suggest that magnetic susceptibility can be used as a viable tool in iron and carbon cycling studies.Key Points Microbial mediated iron-reduction can result in the precipitation of magnetite Higher magnetic susceptibility occurs within zones of iron-reduction Magnetic susceptibility is a viable tool in iron and carbon cycling studies