REVEGETATION OF MINE WASTE DUMP USING PHOSPHATE COATING AND ARTIFICIAL SOIL

Sulfides, common minerals in mine waste, are oxidized producing acid mine drainage (AMD) upon being exposed to oxidation environment. The AMD causes the acidification and metal contamination of soil and water, the damage of plant and the deterioration of landscape in the surrounding area. Revegetation of mine waste dump is one of commonly adopted strategies to reduce the AMD generation and the contaminant migration. However, the revegetation is frequently failed due the high acidity, the toxic metal content, the low nutrient status and the coarse texture of the surface soil. We developed a revegetation method consisting of phosphate coating, neutralization layer and artificial soil and the method was successfully practiced in the field. The 0.01M phosphate solution was applied on the surface to form the Fe-phosphate coating on the sulfide surface, which worked as a physical barrier to prevent contacting oxidants to the sulfide surface. After the coating treatment, a neutralization layer containing 50 % of organic matter, 15 % of dolomite powder and 35 % of soil was constructed at 2 cm thickness to neutralize the rising acidic capillary water from the subsurface and to remove the dissolved oxygen from the percolating rain water. Finally, an artificial soil layer containing seeds, organic matter, nutrients and soil was constructed at 3 cm thickness on the top. The coating treatment with 0.01M phosphate solution reduced about 80 % of AMD production. One gram of neutralization layer material neutralized 1L of pH 3 H₂SO₄ solution to pH 6 and the material completely removed the dissolved oxygen (7.8 mg L^-1) from a tap water within 80 minutes during the reaction of 1material and 10water in a beaker. The plant growth of the area planted by the method is under normal state during last 1 year but the plant of the area planted by seeding and straw mulching died 2 months after germination.