Geochemistry Of Heavy Metals Release In Coal Gangue During Weathering

Coal gangue deposited in the open air for long-term or used by landfill would affected the surrounding environment under the weathering. Taking Sangshu ping and Liao yuan coal gangue of shan’xi province as the research object, researched the physical weathering(coal gangue particle size) and the chemical weathering(leaching, freezing and thawing, soak) effects on pollutants release of coal gangue. Combined with leaching experiment, the freeze-thaw cycle test and immersion test to analyse the particle size and sulfur content of coal gangue in the influence of pollutants release and fraction characteristics of heavy metals in the process of freezing and thawing cycle, explained the geochemical mechanism of pollutants release of coal gangue. At last, give the potential ecological risk of the release of pollutants in weathered gangue.1. Under the leaching, HCO3-、Cl-、K+、Ca2+、Mg2+、Cd、Fe、Mn、Ni、Zn all present quick release, concentration of which show sharp drop in the early stage of the leaching and gradually tend to be stable at later leaching. Particle size has a greater influence on the concentration leaching liquid constants, the smaller the particle size, the faster the constants release. Leaching liquid of high sulfur content of coal gangue inhibit the release of its constant composition, promote the release of the heavy metal elements.2. Freeze-thaw weathering affect the occurrence form of heavy metals directly. When the intensity of freeze-thaw cycles is stronger, the proportion of exchangeable form of As, Cd, Cu transform from of organic state is higher, transformation proportion from iron-manganese state of Cr to carbonate state is higher, transformation proportion from iron-manganese of Pb to the exchangeable state is higher, transformation proportion from organic state to carbonate state is smaller.3. Freeze-thaw weathering effect pollutants release of coal gangue directly, the higher the intensity of freezing and thawing, the easier the mineral crystal lattice of the As, Cd, Cr, Cu, Pb to be leached, the easier to make the leaching concentration is much higher than which is under low intensity.4. Freeze-thaw intensity and particle size affect the geochemistry of coal gangue-water. The smaller the particle size and the higher the intensity of freezing and thawing, the much release of dissolved minerals make mineral saturation index of leaching liquid increase apparently.5. Under the freeze-thaw weathering, the evaluation results of RAC ecological risk index for heavy metals in coal gangue: Ni > Cd > Cu > Pb > As > Cr. The stronger the intensity of freezing and thawing, heavy metals As, Cd, Cu, Pb RAC potential risk index is higher. After freeze-thaw, the coal gangue was immersed by water, the results of Hakanson potential ecological risk index for soak solution is high at first then decrease, and the result of Hakanson potential ecological risk index was that: Cd > Cu > As > Pb > Cr.