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Secondary Mineral Coating Formation and Metal Sequestration in Soils Developing from Mine Spoil Pre- and Post-Treatment with Lime

Cole, Kortney Ann
http://orcid.org/0000-0002-5862-0734
http://rave.ohiolink.edu/etdc/view?acc_num=kent1630329926126993

Abstract Details

2021, MS, Kent State University, College of Arts and Sciences / Department of Earth Sciences.
Acid mine drainage (AMD) is one of the most serious environmental threats to water resources in the world. Mining operations create conditions that expose pyrite where it is susceptible to weathering by oxidative dissolution. Over time, soils develop from the mine spoil containing sulfide minerals and trace metals such as Fe, Mn, Zn, Al, Cu, and As. Adding alkalinity to the soil slows the oxidation rate of pyrite and promotes the precipitation of secondary minerals, particularly iron oxides, that may sorb metal ions and decrease porosity within the soil preventing further sulfide oxidation. This work is part of a recently completed pilot project which examined the efficacy of lime slurry as a non-point source treatment of pyrite-rich ~40-year-old mine spoil in the Huff Run Watershed (Mineral City, Ohio). In the current work, 12 thin sections prepared from two field sites (BP, an embankment located near a tributary to the Huff Run (subwatershed HR-25) with heavy understory vegetation and trees; and BY, a conical hill of mine spoil located northwest and upslope of the BP site with large trees, many dead or dying, but virtually no understory vegetation) collected along a depth profile and two laboratory columns of composite soils, which were either untreated or treated with a lime slurry. The impact of treatment on the formation and texture of secondary mineral coatings and trace metal sequestration was examined by Scanning Electron Microscopy (SEM) with Energy Dispersive Spectroscopy (EDS) element mapping. The image analysis software ImageJ was used to perform a quantitative analysis to determine the particle characteristics, surface area, coverage, and thickness of secondary mineral coatings and aggregates in the soils. Element correlation scatterplots created with the ScatterJn plugin were used to examine the association between trace metals and mineral surfaces. Results of this work show that lime addition significantly increased secondary coating coverage compared to that in untreated field soils: BP 00-10 cm (21.3 +/- 35.5 mm2 ; 278.5 +/- 265.1 mm2), BP 70-80 cm (29.9 +/- 0.0 mm2 ; 39.7 +/- 0.6 mm2); BY 00-10 cm (54.8 +/- 32.3 mm2; 133.5 +/- 7.0 mm2); BY 40-50, 60-70 cm (50.6 +/- 17.1 mm2; 135.8 +/- 0.0 mm2). Coating coverage did not change significantly in C1 (52.0 +/- 24.3 mm2; 67.4 +/- 13.2 mm2) nor C2 (30.6 +/- 18.7 mm2; 27.3 +/- 29.5 mm2) soils after lime addition. Lime treatment significantly increased Fe-(hyrd)oxide coating thickness in BP 70-80 cm (0.56 +/- 1.14 µm; 0.58 +/- 0.89 µm); BY 00-10 cm (0.58 +/- 0.74 µm); BY 40-50, 60-70 cm (0.67 +/- 1.36 µm; 1.95 +/- 2.06 µm); and C2 (0.51 +/- 0.70 µm ; 1.02 +/- 1.36 µm) soil. Coating thickness did not significantly increase in BP 00-10 cm (0.86 +/- 1.89 µm; 0.90 +/- 2.20 µm) and C1 (0.55 +/- 0.47 µm; 1.05 +/- 1.92 µm) after lime treatment. Post treatment oxide coating fraction trace metals Cr, Zn, and As increased in BY; Co, Ni, Zn, and As increased in BP; Co, Cr, and Cu increased in C1; Co and As increased in C2. Fe abundance in oxide coatings were higher after treatment in samples: BY (27.2 +/- 2.6 wt.%; 27.3 +/- 9.1 wt.%); BP (23.6 +/- 9.2 wt.%; 30.2 +/- 10.0 wt.%); C2 (30.0 +/- 2.7 wt.%; 33.8 wt.%). Fe abundance decreased in C1 (17.9 wt.%; 23.3 +/- 14.9 wt.%) soil post-treatment. Coating formation also likely played a role in particle aggregation. Ca-rich phases unique to treated soils with similar element distribution to calcite and gypsum were observed. Lime slurry treatment in soils developing on historic mine spoil is effective at both promoting oxide coating formation and metal sequestration, though our investigation demonstrates that soil heterogeneity can significantly affect the degree to which coating formation and metal sequestration occurs. Residual sulfide bearing coal, rocks, and minerals provide zones of increased weathering (and subsequent metal loading) across a depth profile that may complicate planning effective lime application, as was the case between BP and BY. Factors like soil permeability and preferential flow paths within soil were likely important influences controlling delivery of lime slurry to regions in field soils, likewise, the pump rate for water flow in the column experiments may have decreased the residence time of pore water, limiting coating formation. Based on this work, the effect of lime treatment on the coverage, thickness, and metal sequestration capacity of Fe-oxide coatings would likely be exacerbated with more concentrated lime applications and should be considered a viable option for treatment of mine spoil soils.
David Singer (Advisor)
Jeremy Williams (Committee Member)
Kuldeep Singh (Committee Member)
135 p.
Geochemistry; Geology
Acid Mine Drainage; AMD; SEM-EDS; Coal mine spoil; point-source treatment; lime; soil remediation; trace metal contamination; ImageJ; microscopy; ScatterJn

Recommended Citations

Citations

  • Cole, K. A. (2021). Secondary Mineral Coating Formation and Metal Sequestration in Soils Developing from Mine Spoil Pre- and Post-Treatment with Lime [Master's thesis, Kent State University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=kent1630329926126993

    APA Style (7th edition)

  • Cole, Kortney. Secondary Mineral Coating Formation and Metal Sequestration in Soils Developing from Mine Spoil Pre- and Post-Treatment with Lime. 2021. Kent State University, Master's thesis. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=kent1630329926126993.

    MLA Style (8th edition)

  • Cole, Kortney. "Secondary Mineral Coating Formation and Metal Sequestration in Soils Developing from Mine Spoil Pre- and Post-Treatment with Lime." Master's thesis, Kent State University, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=kent1630329926126993

    Chicago Manual of Style (17th edition)

kent1630329926126993
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This open access ETD is published by Kent State University and OhioLINK.