The purpose of this research is to characterize reactive Fe mineral coatings in redox transition zones of a contaminated site. An anaerobic 60 foot core was collected from the Chambers Works Site in Deepwater, NJ. Two inch subsamples were used to evaluate redox transition zones using bulk composition, redox potential, pH, volatile organic carbon in the headspace, as well as microbial community. A suite of complementary analyses is being applied to characterize the surface chemistry in the four transition zones. The analyses include sequential extraction (phases and speciation), x-ray diffraction (mineralogy), x-ray fluorescence (composition), field-emission scanning electron microscopy (surface morphology down to the nm scale) with energy dispersive analysis (surface composition), and bench-scale experiments. Evidence from multiple lines suggest a clear trend in reactive iron (II)/(III) mineral coatings throughout transition zones. Bulk minerals observed included quartz, muscovite, clinochlore, and zeolite. Other zones have also included albite and anorthite. Using the suite of tools, reactive iron mineral coatings involve the iron (II) minerals pyrite, mackinawite, pyrrhotite, and siderite in the transition zone between depths from 21’ to 22.8’. Ferrihydrite, goethite, and lepidocrocite were the dominant iron (III) minerals in zone 31’ to 34.3’, while pyrite, greigite and gypsum were the most abundant mineral coating in zone 13’ to 15’. The presence of reactive mineral coatings through the redox transition zones is a strong indicator of Fe<sup>2+</sup>/Fe<sup>3+</sup> cycling. Therefore, further studies on abiotic degradation of the halogenated solvents present will be investigated.

Characterizing reactive iron mineral coatings in redox transition zones

254th National Meeting (2017)

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