Reactive iron mineral coatings in redox transition zones play an important role in contaminant attenuation. These mineral coatings include poorly crystalline to crystalline iron sulfides, carbonates, and oxyhydroxides, and are a signature of the biogeochemical processes occurring. To better understand these processes, reactive iron mineral coatings were characterized in an anaerobic 18 m (60 ft) core collected from a contaminated industrial site. This study targets two redox transition zones uncovered in the core. A suite of complementary analyses was applied to distinguish the surface coating mineralogy using X-ray diffraction, X-ray fluorescence, and field-emission scanning electron microscopy with energy dispersive X-ray analysis. In the shallowest transition zone running through an aquifer with clay lenses, framboidal pyrite and greigite were observed in the clay lenses, while iron (III) phases in the aquifer included goethite, ferrihydrite, lepidocrocite, and hematite. In a deeper aquitard transition zone, iron sulfides were found as flaky aggregates of mackinawite, pyrite, and pyrrhotite. In addition, the iron (II)/(III) mineral magnetite was also observed in this same area. Moving deeper into this zone, the most abundant coatings were found to shift to the iron (III) oxyhydroxide minerals. Overall, reactive mineral coatings observed are important surfaces contributing to the natural attenuation processes in redox transition zones.

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氧化还原过渡区中活性铁矿物涂料的表征

氧化还原过渡区的反应性铁矿物涂层在污染物衰减中起重要作用。这些矿物涂层包括结晶性差至结晶性的硫化铁，碳酸盐和羟基氧化物，是发生的生物地球化学过程的标志。为了更好地理解这些过程，活性铁矿物涂层的特征是从受污染的工业场所收集的18 m（60 ft）厌氧芯。这项研究的目标是在核心中发现的两个氧化还原过渡区。应用了一系列补充分析，以使用X射线衍射，X射线荧光和具有能量色散X射线分析的场发射扫描电子显微镜来区分表面涂层的矿物学。在最浅的过渡带中，穿过带有粘土透镜的含水层，在粘土晶状体中观察到黄铁矿黄铁矿和钙铁矿，而含水层中的铁（III）相包括针铁矿，三水铁矿，纤铁矿和赤铁矿。在更深的aquitard过渡带中，发现硫化铁为麦基钠铁矿，黄铁矿和黄铁矿的片状聚集体。另外，在该区域也观察到了铁（II）/（III）磁铁矿。深入到该区域，发现最丰富的涂层向羟基氧化铁（III）矿物转移。总体而言，观察到的反应性矿物涂层是重要的表面，有助于氧化还原过渡区的自然衰减过程。硫化铁被发现为麦基钠铁矿，黄铁矿和黄铁矿的片状聚集体。另外，在该区域也观察到了铁（II）/（III）磁铁矿。深入到该区域，发现最丰富的涂层向羟基氧化铁（III）矿物转移。总体而言，观察到的反应性矿物涂层是重要的表面，有助于氧化还原过渡区的自然衰减过程。硫化铁被发现为麦基钠铁矿，黄铁矿和黄铁矿的片状聚集体。另外，在该区域也观察到了铁（II）/（III）磁铁矿。深入到该区域，发现最丰富的涂层向羟基氧化铁（III）矿物转移。总体而言，观察到的反应性矿物涂层是重要的表面，有助于氧化还原过渡区的自然衰减过程。