EFFECT OF ORGANIC AND INORGANIC RESIDUES ON THE SOLUBILITY OF TRACE ELEMENTS AND PHYTOTOXICITY OF MINING WASTE

摘要

A polluted soil from sulphur-mine wastes was amended with 17 combinations of inorganic (marble sludge) and organic (compost and vermicompost) materials. The leachates and soil solutions of the soil with and without amendments were analysed, and their phytotoxicity was estimated from the germination and root-elongation indexes of lettuce seeds. The leachates and soil solutions of the soil without amendments were highly concentrated in major and trace elements and consequently toxic (no seed germinated). When the soil was amended only with marble sludge, CaCO_3 neutralized the H~(+) present in the leachates and soil solutions, the pH abruptly rose, the concentration of soluble major and trace elements declined sharply, and the indexes of germination and root elongation clearly increased. When the soil was amended only with compost and vermicompost, H~(+) was not neutralized, and the concentration of pollutants in leachates and soil solution remained very high, even higher than in the soil without amendments, and no seed germinated. When the soil was amended with organic and inorganic materials, the results were similar to those of the soil amended only with marble sludge, although, especially the leachates of the soils amended with the lowest quantity of marble sludge (40 g kg~(-1) dry soil) showed higher concentrations in dissolved elements and greater toxicity. Consequently, the polluted soil from sulphur-mine wastes should be amended fundamentally with inorganic materials rich in CaCO_3 content, and the quantity added should be higher than 40 g CaCO_3 kg~(-1) dry soil. When organic amendments are added to the polluted soil, the management of leachates should be careful in order to minimize the spread of pollutants and the risk of contamination of groundwater and surrounding soils.