You are here:
Remediation of an acidic mine spoil: Miscanthus biochar and lime amendment affects metal availability, plant growth, and soil enzyme activity
Novak, J., J. Ippolito, T. Ducey, D. Watts, K. Spokas, K. Trippe, G. Sigua, AND Mark G Johnson. Remediation of an acidic mine spoil: Miscanthus biochar and lime amendment affects metal availability, plant growth, and soil enzyme activity. CHEMOSPHERE. Elsevier Science Ltd, New York, NY, 205:709-718, (2018). https://doi.org/10.1016/j.chemosphere.2018.04.107
Biochar, the charcoal-like material made from heating biomass in the absence of oxygen, has been proposed as a remedial amendment for metal contaminated soils such as mine spoils. The notion is that by adding biochar and other amendments (e.g., lime and biosolids) that sufficient remediation can be provided so that plants can be established and grow to stabilize the contaminated soils and reduce exposure risks. To evaluate this hypothesis biochar was made from Miscanthus (Miscanthus giganteus), a bioenergy plant, that was pyrolyzed at 700 °C and added to soil at 0, 1, 2.5 and 5% (w/w) to mine spoil soils from the Formosa Mine (located outside Riddle, OR). Other amendments included no lime, lime and N-P-K fertilizer. Soils with and without amendments were placed in plastic pots and each was seeded with Blue Wildrye (Elymus glaucus). The plants were grown in a greenhouse for 60 days. At the end of the study, each pot was leached with deionized water, and the leachate analyzed for pH, electrical conductivity (EC), dissolved organic carbon (DOC) and soluble metal concentrations. The soils were also analyzed for extractable metals to assess the effects of the amendments and for soil enzymes to determine the effects on soil microbial processes. As expected, lime additions significantly reduced extractable metal concentrations (i.e., Al, Cu, and Zn), and increasing biochar rates alone significantly reduced leachate DOC concentrations and leachable metal concentrations. Surprisingly, Miscanthus biochar by itself, was not particularly effective at improving soil pH and soil health characteristics, but when combined with lime, the combination was capable of further reducing extractable metals and improving soil enzyme activity (i.e., soil health). These results provide improved guidance for using biochar and lime as soil amendments to improve soil health to support revegetation of metal contaminated mine spoils. This Article contributes to SHC 3.63.2.
Biochar may be a tool for mine spoil remediation; however, its mechanisms for achieving this goal remain unclear. In this study, Miscanthus (Miscanthus giganteus) biochar was evaluated for its ability to reclaim acidic mine spoils (pH < 3) through reducing metal availability, improving soil microbial enzymatic activity, and initial growth of grass seedlings. Biochar was applied at 0, 1, 2.5 and 5% (w/w) along with lime/no lime and fertilizer additions. Blue Wildrye (Elymus glaucus cv. ‘Elkton’) was planted and later the shoots and roots were collected and metal concentrations determined. Afterwards, each pot was leached with deionized water, and the leachate analyzed for pH, electrical conductivity (EC), dissolved organic carbon (DOC) and soluble metal concentrations. After drying, the spoil was extracted with 0.01 M CaCl2 and Mehlich 3 (M3) to determine extractable Al, Cu, and Zn concentrations. Additionally, microbial activity was measured using a fluorescent β-glucosidase and N-acetyl-β-D-glucosaminidase assay. Spoil treated with lime and biochar had significantly greater pH and EC values. Significantly greater β-glucosidase activity occurred only in the 5% biochar plus lime treatment, while N-acetyl-β-D-glucosaminidase activities were not altered. Metal concentrations in rye shoot and roots were mixed. Lime additions significantly reduced extractable metal concentrations. Increasing biochar rates alone significantly reduced leachate DOC concentrations, and subsequently reduced leachable metal concentrations. Surprisingly, miscanthus biochar, by itself, was limited at mitigation, but when combined with lime, the combination was capable of further reducing extractable metal concentrations and improving β-glucosidase enzyme activity.
Record Details:Record Type: DOCUMENT (JOURNAL/PEER REVIEWED JOURNAL)
Organization:U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
NATIONAL HEALTH AND ENVIRONMENTAL EFFECTS RESEARCH LABORATORY
WESTERN ECOLOGY DIVISION
ECOLOGICAL EFFECTS BRANCH