|IPPOLITO, JAMES - Colorado State University|
|Watts, Donald - Don|
|JOHNSON, MARK - Us Environmental Protection Agency (EPA)|
Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/17/2018
Publication Date: 5/2/2018
Citation: Novak, J.M., Ippolito, J.A., Ducey, T.F., Watts, D.W., Spokas, K.A., Trippe, K.M., Sigua, G.C., Johnson, M.G. 2018. Remediation of an acidic mine spoil: Miscanthus biochar and lime amendment affects metal availability, plant growth and soil enzymatic activity. Chemosphere. 205:709-718. https://doi.org/10.1016/j.chemosphere.2018.04.107.
Interpretive Summary: Biochars are being considered as an amendment for mine spoil reclamation to improve plant growth conditions. Typically, poor plant growth occurs in mine spoils because they can be acidic and/or contain heavy metal levels that are toxic to plants. It is desirable to have better plant growth on mine spoils in order to minimize erosion and mobilization of heavy metals into water bodies. Unfortunately, the ability of biochars to improve plant growth on mine spoils has not been well researched. Hence, we conducted a greenhouse study of a biochar produced from Miscanthus (a grass) to potentially improve an acidic mine spoil (pH < 3) that also contained plant harmful levels of zinc (a heavy metal). We applied biochar; lime and fertilizer in various combinations to the mine spoil and planted rye grass. After 8 weeks in the greenhouse, we measured the amount of rye grass growth, the mine spoils acidity, and zinc levels. We found that rye grass growth was improved with lime and fertilizer alone, and the biochar, by itself, was not particularly effective at raising the spoil pH or binding soil zinc. However, dissolved organic carbon solublized from the biochar did bind soluble metals that could assist with better rye grass growth. We concluded this Miscanthus biochar was partially effective at improving health characteristics in the Formosa mine spoil. Lime proved to be the better choice of an amendment.
Technical Abstract: Biochar is proposed as an amendment for mine spoil remediation; however, its effectiveness at achieving this goal remains unclear. Miscanthus (Miscanthus giganteus) biochar was tested for potentially improving acidic mine spoil (pH < 3; Formosa mine near Riddle, Oregon) health conditions by sequestering excessive metals, improving enzymatic activity, and supporting Blue Wildrye (Elymus glaucus) growth. Biochar was applied at 0, 1, 2.5 and 5% (weight/weight) along with lime/no lime and fertilizer. Rye grass was planted in pots and harvested after 60 days of growth. At termination, each pot was leached with deionized water, and the leachate analyzed for pH, electrical conductivity (EC), dissolved organic carbon (DOC) and soluble metal concentrations. Microbial diversity using phospholipid fatty acid (PLFA) technique and ß-glucosidase and N-acetyl-ß-D-glucosaminidase activity were measured in moist soils. After drying, the spoil was extracted with 0.01 molar calcium chloride and Mehlich 3 (M3) to determine extractable aluminum (Al), copper (Cu), and Zinc (Zn) concentrations. Biochar additions to spoil had a minor impact while lime significantly reduced salt and M3 extractable Al, Cu, and Zn concentrations. Increasing biochar rates alone significantly reduced leachate DOC concentrations, and subsequently reduced leachable metal concentrations. PLFA analysis showed mostly Gram negative and positive microbial communities exist in spoils. Significantly greater ß-glucosidase activity occurred only at the 5% biochar plus lime treatment, while N-acetyl-ß-D-glucosaminidase activity was not impacted. Lime was an effective remediation agent for improving mine spoil health; concomitantly, Miscanthus biochar was particularly effective at sequestering both soluble Cu and Zn concentrations.