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Acid mine drainage is a serious and pervasive threat to surface and groundwater quality in the USA. Recent research has indicated that phosphate can be effective at immobilizing Fe and inhibiting the production of acid associated with the oxidation of pyritic mine wastes. Four phosphate materials were replicate tested for their ability to inhibit acid production from pyritic coal overburden using a soxhlet humidity cell leaching technique. These materials included two apatite ores (Comineo ore and Texas Gulf ore) at an application rate of 30 g kg−1 by weight apatite [Ca5(PO4)3OH] and two byproducts of the phosphate industry (Cominco waste and Stauffer sludge) at rates of 10, 30, and 50 g kg−1 apatite by weight. Results of leachate analyses indicate that all phosphate sources at all rates of application resulted in significant (P ≤ 0.05) decreases in titratable acidity vs. a control Acidity reductions ranged from a low of 7% for samples treated with Cominco waste (10 g kg−1) to a high of 67% for Texas Gulf ore‐treated samples. Texas Gulf ore, Stauffer sludge (10, 30, and 50 g kg−1) and Cominco waste (10, 30, and 50 g kg−1) significantly reduced dissolved total Fe concentrations in leachate, with Stauffer sludge (50 g kg−1) and Texas Gulf ore producing the most notable diminutions (62 and 63%, respectively). Maximum decreases in sulfate (SO2−4) concentrations of 26, 20, and 25% were achieved by applications of Texas Gulf ore and Stauffer sludge (30 and 50 g kg−1), respectively. The more effective overall performance of the Stauffer sludge and Texas Gulf ore was attributed to the considerably greater relative surface area and P solubility of these amendments. Results of a scanning electron microscope examination of amendments corroborate these findings.

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Abandoned coal waste exhibits adverse physical and chemical properties which preclude vegetation establishment. Coal waste from a site in Montana was acidic (pH 2.8), black, 85% coarse fragments and had a low water holding capacity. Incorporation of cement kiln dust (CaO) and limestone (CaCO3) to 35 cm at rates recommended by a weathering procedure neutralized coal waste acidity in the surface 10 cm. Incorporating CaO to 100 cm neutralized coal waste to the 30‐cm depth. Seeded vegetation was healthy and vigorous where lime was applied, though percent canopy cover and aboveground production were low after 2 yr. Application of kiln dust five times the recommended rate significantly reduced plant performance. Application of coversoil significantly increased plant performance compared to sites without coversoil by providing a more suitable germination medium. Increasing coversoil application from 15 to 30 cm did not significantly increase plant performance. Depth of root penetration was a function of depth of lime incorporation and coversoil thickness. Root distribution was neither confined to nor concentrated in the coversoil. Root proliferation into limed coal waste was similar to that present in overlying coversoil.