铁锰双金属材料在不同pH条件下对土壤As和重金属的稳定化作用

pH是影响土壤As和重金属赋存形态及稳定化过程的重要因素,本文以人工合成的铁锰双金属材料(FMBO)为研究对象,研究了其在不同pH条件下对3种As和重金属复合污染土壤的稳定化作用,同时探讨了材料添加对土壤pH和酸碱缓冲性的影响.结果表明,As、Pb元素分别在土壤pH 3~9的中性偏酸性条件、pH 5~10的中性偏碱性条件下较为稳定,Cd、Zn、Cu在pH为7~11的碱性条件下浸出浓度较低.在碱性条件下,FMBO材料自身稳定性及稳定化作用均优于酸性条件,在As和重金属稳定的最适pH范围内,随着材料添加量增加,稳定化效率逐渐升高,其对As、Pb、Cd、Zn、Cu的稳定化效率最高分别能达到92.7%、100%、97.0%、88.7%、82.7%.添加FMBO材料可使土壤pH值升高,并能够提高土壤的酸缓冲能力,对As和重金属的长期稳定性有促进作用,而对土壤碱缓冲作用影响较小.从浸出元素的相关关系可以看出,Fe元素对土壤中As的稳定性有重要作用,Pb、Cd、Zn、Cu的稳定性受土壤pH影响较大.

Stabilization Effects of Fe-Mn Binary Oxide on Arsenic and Heavy Metal Co-contaminated Soils Under Different pH Conditions

pH is one of the most important factors affecting speciation and stabilization of arsenic and heavy metals in soil. In this study, Fe-Mn binary oxide (FMBO), synthesized by redox and precipitation reactions, was taken as the research object to evaluate its stabilization effects on As, Pb, Cd, Zn, and Cu in three types of soils under different pH conditions and to study the impacts on soil pH and buffering capacity. The results showed that the leaching concentrations of As and Pb were lower in the pH range of 3-9 (neutral and weak acidic) and 5-10 (neutral and weak alkaline); and Cd, Zn, and Cu were stable in the pH range of 7-11 (alkaline). The stability and stabilization effects of FMBO were better under alkaline conditions than acidic. In the optimal pH range, the optimum stabilization efficiency of FMBO could reach 92.7%, 100%, 97.0%, 88.7%, and 82.7% for As, Pb, Cd, Zn, and Cu, respectively. In addition, FMBO addition could increase soil pH and the acid buffering capacity moderately, which improved heavy metal stabilization and made it more suitable for acid soils and areas with more acid rain. From the correlation of contaminants and soil elements in the leachates, Fe played an important role in As stabilization, and pH had a great influence on the stabilization of Pb, Cd, Zn, and Cu.