煤矸石风化物不同粒级中重金属镉含量及其形态变化

对抚顺西露天矿煤矸石山表层煤矸石风化母岩进行多点取样,风化物筛分成>2 mm、2～0.25 mm和<0.25 mm等3个粒级,分析测定了矸石山表层母岩及其风化物不同粒级中Cd含量及其形态变化特征.结果表明:煤矸石母岩及其风化物中cd含量超过土壤环境质量2级标准,页岩、泥岩及其风化物pH值7.2～8.6,但燃后泥岩pH值4.9.碳质页岩2～0.25 mm粒级风化物中Cd损失最多,为73.6%;<0.25 mm细粒级Cd损失较少,为17.0%,这与细颗粒的表面吸附作用有关;泥岩及其各粒级风化物Cd元素不易损失,其Cd含量变化也相对较小;但燃后泥岩风化物中的Cd较容易损失.煤矸石风化物各样品类型中的Cd均以残渣态为主,可还原态和弱酸可提取态所占比例次之,可氧化态所占比例最小.弱酸可提取态Cd在细颗粒风化物中所占比例较高.

Content and speciation changes of Cd in different particle size of coal waste

The weathered coal wastes were sampled at the surface layer in Fushun West Opencast coal mine dump, the weatherings were divided into 3 particle size fraction of>2 ram, 2～0.25 mm and <0.25 mm. The contents of Cd and its chemical speciation were determined in mother rocks and their different particle fractions of coal waste weathering product. The results show that the contents of Cd exceed the soil environment quality standard of 2th level, the pH of shale, mudstone and their weathering products is from 7.2 to 8.6, but the pH of burned mudstone is 4.9. In the carbonaceous shale weathering product of 2～0.25 mm, Cd lose is the most, which is 73.6%; in <0.25 mm grade, Cd loses are less, which is 17.0%, that may be related to the fine-grains' surface adsorption; the Cd is not easy to lose in mudstone weathering product, and the Cd contents also changes less relatively; but in burned mudstone weather-ing product, Cd is easy to loss. In all types of coal waste weathering product samples, the Cd mainly exists in residual speciation; the Cd in reduced speciation and extractable speciation from weak acid is less; and oxidation speciation is the least. The Cd in extract-able speciation from weak acid has the high proportion in <0.25 mm weathering particles.