STABILIZATION AND REVEGETATION OF METAL SMELTER WASTES IN POLAND

摘要

Water and wind erosion of toxic zinc and lead smelter waste is one of the most urgent environmental problems to be solved in the Silesia region of Poland. Over 87 million Mg of these materials were disposed of in uncontrolled piles leading to soil, water, and air pollution in extensively populated areas. Welz and Doerschel process Pb/Zn smelter wastes were stabilized in the summer of 1994 by application of heavy loads of calcium carbonate (30 Mg/ha), calcium oxide (1.5 - 15 Mg/ha), and municipal sewage sludge (150 - 300 Mg/ha), followed by seeding with a mixture of acid- and salt-tolerant grass species selected in a pot experiment. Vegetation was successfully established on 85% of the Welz material demonstration plot area (0.5 ha), even though it was initially high in water-soluble zinc, lead, and cadmium ranging from 0.4 to 1311,0.1 to 5.8, and 0.05 to 55 mg/kg, respectively. Standing biomass approached 2.0 to 2.5 Mg/ha on the stabilized Welz waste at the end of the second growing season. Laboratory experiments demonstrated that amendments with CaO can effectively reduce metal solubility to ppb levels in the wastes. However, the use of CaCO_3 (up to 10% w:w), due to limited solubility and occlusion with metal hydroxides, allowed phytotoxic levels of zinc (30 mg/1) and cadmium (1.7 mg/1) in soil solution. The revegetation of much of the Doerschel material area failed because of extremely high salinity (16 dS/m), high content of water soluble metals (Cd in particular), and heavy compaction. The area was capped with waste lime and retreated with sludge (300 Mg/ha) in 1995, and preliminary results indicate greater success at stabilizing this exceptionally harsh material. The observed plant response to sludge and lime indicates this approach to be an environmentally beneficial technology as compared to the traditional methods utilizing topsoil covers or heavily engineered material processing or encapsulation approaches.