添加稳定剂对尾矿土中砷形态及转换机制的影响

土壤中As的不同存在形态影响着其毒性、可移动性、生物有效性,且产生不同的环境影响.本研究以粉煤灰、干化污泥、硫酸亚铁、碎花生壳为稳定剂,探讨其对土壤As的稳定化效果以及p H、有机质和阳离子交换量与土壤As形态的关系.结果表明添加稳定剂后,土壤p H及有机质含量上升,残渣态砷含量升高.添加10%粉煤灰、10%干化污泥后,可交换态As、碳酸盐结合态As、铁锰氧化物结合态As、有机结合态As分别下降了34.2%、17.5%、19.9%、53.7%,并转化为残渣态As,其含量增长了1.14%.当同时添加10%粉煤灰、10%干化污泥和1%硫酸亚铁后,土壤中可交换态As、碳酸盐结合态As、铁锰氧化物结合态As、有机结合态As含量的降幅分别为62.3%、55.2%、29.6%、58.2%,残渣态As含量增加8.1%.添加10%粉煤灰、10%干化污泥、1%硫酸亚铁和1%粉碎花生壳后,可交换态As下降最显著,最大降幅为73.3%.施用适量的粉煤灰、干化污泥、硫酸亚铁能使土壤中的可交换态、碳酸盐结合态、铁锰氧化物结合态、有机结合态As的一部分转化为残渣态As,降低其毒性.提高p H,残渣态As含量上升,可交换态As、碳酸盐结合态As、铁锰结合态As、有机结合态As含量下降,As在接近中性的环境中稳定性最好;提高有机质含量,碳酸盐结合态As与残渣态As含量上升,可交换态As、铁锰结合态As、有机结合态As含量下降,有机结合态As含量下降明显;阳离子交换量上升,残渣态As含量上升,可交换态As、碳酸盐结合态As、铁锰结合态As、有机结合态As含量下降.

Effect of Stabilizer Addition on Soil Arsenic Speciation and Investigation of Its Mechanism

Arsenic toxicity, mobility and bioaccessibility are influenced by its different speciation in soil, which exerts different impacts on the environment. In this study, coal fly ash, dried sludge, ferrous sulfate and broken peanut shell were used as stabilizers to investigate their stabilizing effects on As in soil as well as relationships between pH, soil organic matter content, cation exchange capacity and speciation of soil As. The results showed rise in soil pH, soil organic matter content and residual arsenic content after the addition of stabilizers. Addition of 10% coal fly ash and 10% dried sludge led to the decrease in the content of exchangeable As, carbonate bound As, Fe-Mn oxide bound As, organic bound As by 34.2%, 17.5%, 19.9%, 53.7%, respectively. Addition of ferrous sulfate could preferably stabilize As in soil. When 10% coal fly ash, 10% dried sludge and 1% ferrous sulfate were added concurrently, the decrease in the content of exchangeable As, carbonate bound As, Fe-Mn oxide bound As, organic bound As was 62.3%, 55.2%, 29.6%, 58.2%, respectively, with an increase in residual arsenic content by 8.1%. After the addition of 10% coal fly ash, 10% dried sludge, 1% ferrous sulfate and 1% broken peanut shell, a most conspicuous decrease in the content of exchangeable As by 73.3% was observed. Appropriate application of coal fly ash, dry sludge and ferrous sulfate converted a proportion of exchangeable, carbonate bounded, Fe-Mn bounded, organic bounded As into residual As, which reduced As''s toxicity. The rise in pH led to increasing residual As content and decreasing exchangeable As, carbonate bounded As, Fe-Mn bounded As and organic bounded As content, and As was most stable at the approach of neutral condition. The rise in organic matter content led to increasing carbonate bounded As and residual As content and decreasing exchangeable As, Fe-Mn bounded As, organic bounded As content. The rise in cation exchange capacity led to increasing residual As content and decreasing exchangeable As, carbonate bounded As, Fe-Mn bounded As and organic bounded As content.