Soil Amendments Promote Vegetation Establishment and Control Acidity in Coal Combustion Waste
The effects of adding various soil amendments and a pyrite oxidation inhibitor to aid in the establishment of vegetation and to reduce acid drainage (AD) from coal fly ash and coal reject (FA + CR*) were assessed in an outdoor mesocosm study. Preliminary greenhouse experiments and field observations at the U.S. Department of Energy’s Savannah River Site (SRS) indicated that plants would not survive in this material without altering its physical and chemical characteristics. Samples of mixed FA + CR were obtained from a field site at the SRS. The following treatments were used: Biosolid only (Treatment A), Biosolid + Surfactant (Treatment B), Topsoil + Surfactant (Treatment C), and Biosolid + Topsoil + Surfactant (Treatment D). Leaching was induced due to inadequate rainfall. Loblolly pine seedlings (Pinus taeda) inoculated with ectomycorrhizal fungi — Pisolithus tinctorius (Pt) and Scleroderma cepa (Sc) — were transplanted into each mesocosm tank. Soil solution samplers were installed in each unit at 15 and 41 cm depths. Samples were taken periodically and measured for pH, EC, and other parameters.
The results indicate that the addition of amendments can aid in the revegetation of a FA + CR landfill and control AD. Pine seedlings growing in treatments with biosolid application were significantly taller than the treatment without it; however, there were no significant differences concerning diameter, biomass, and plant tissue concentrations of Al, Fe, and Mn for the pines. Biosolid addition also appears to be effective for mitigating proton generation. Sodium lauryl sulfate (SLS) and topsoil addition were not as important to plant survival and growth as biosolid addition; nonetheless, SLS and topsoil addition did not appear to be disadvantageous to growth in the treatment with biosolid addition (Treatment D). Based on leachate data, the topsoil + surfactant treatment had a much lower initial pH (pH ~ 3 or below) than the other treatments, and Al concentrations were correspondingly high. Electrical conductivity, in general, has been decreasing since the inseption of the study and appears to indicate that the addition of biosolid + surfactant (Treatment B) is the most effective treatment for inducing the lowest sulfate and metal concentrations. Preliminary results indicate that the use of amendments is essential for palant growth and establishment in pyrite enriched coal waste sites.
KeywordsSodium Lauryl Sulfate Pyrite Oxidation Coal Combustion Waste Savannah River Site Biosolid Application
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