TY - JOUR
T1 - Characterizing Reactive Iron Mineral Coatings in Redox Transition Zones
AU - Hua, Han
AU - Yin, Xin
AU - Dyer, James A.
AU - Landis, Richard
AU - Axe, Lisa
N1 - Funding Information:
We gratefully acknowledge support for this research through a contract (LBIO-6706/9900403035) with the Chemours Company and Project Managers Ed Lutz and Ed Seger. We also thank the entire team that collected the anaerobic core at the site from DuPont and AECOM.
Publisher Copyright:
©
Copyright:
Copyright 2021 Elsevier B.V., All rights reserved.
PY - 2020/12/17
Y1 - 2020/12/17
N2 - 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.
AB - 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.
KW - FESEM
KW - XRD
KW - abiotic transformation
KW - iron sulfide coatings
KW - mineral coating characterization
KW - redox transition zones
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U2 - 10.1021/acsearthspacechem.0c00233
DO - 10.1021/acsearthspacechem.0c00233
M3 - Article
AN - SCOPUS:85097903474
SN - 2472-3452
VL - 4
SP - 2337
EP - 2346
JO - ACS Earth and Space Chemistry
JF - ACS Earth and Space Chemistry
IS - 12
ER -