| Abstrakt: |
The effects of sewage sludge, lime, and gypsum on the chemical composition of percolate from acidic coal refuse material was studied at a Fulton County, IL, land reclamation site. Treatments consisted of a control, 542 dry Mg ha−1anaerobically digested sewage sludge, 89.6 Mg ha−1lime, 112 Mg ha−1gypsum, and combinations of these amendments. The chemical composition of the percolate collected monthly (1976 to 1980) from suction lysimeters at a 1‐m depth reflected the treatments applied to the coal refuse material. Percolate pH, NH+4‐N and [NO−3+ NO−2]‐N levels were lowest in either the gypsum or control treatments and highest in the sewage sludge treatment. Percolate SO4levels were lowest in either the control or sludge‐amended treatments and highest in the gypsum‐amended treatments. Levels of NH+4‐N and [NO−3+ NO−2]‐N in percolating waters from the sludge‐amended treatments declined with time, while P levels remained at <2.3 mg L−1. Percolate concentrations of Al, Cr, Cu, Fe, and Zn were lowest in the sewage sludge treatment and highest in gypsum‐amended treatments. Metal solubility in the percolate was affected by the chemical composition of the coal refuse material and the applied amendments. Percolate Al, Cd, Cr, Cu, Fe, Ni, and Zn levels were negatively related (P≤ 0.01) to pH in the sludge and sludge + lime treatments. Estimated concentrations of the various metals at a specific pH indicates that the sludge and sludge + lime treatments were very effective in reducing metal leaching when the percolate pH was ≥5.0. The application rates of lime and sewage sludge based on theoretical procedures were effective for about 5 yr. For long‐term (>5 yr) reclamation, the effectiveness of the sludge and sludge + lime treatments would be better maintained by applying more sludge (1050 Mg ha−1) and (900 to 1350 Mg ha−1) + lime (134 to 189 Mg ha−1) initially. The factor of two difference between the theoretical and actual amounts of lime and sewage sludge needed in the field suggests that an added safety factor of one and a half to two for application of these amendments is desirable for long‐term reclamation of coal refuse material. |
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