同步钝化土壤Cd和As材料的筛选

土壤中Cd和As的化学行为相反，导致同时降低土壤Cd和As的有效性成为一个难题.本实验采用先淹水30 d后湿润30 d的培养方法，研究了海泡石（Sep）、铁改性海泡石（IMS）、铁锰改性海泡石（Sep-FM）、钢渣（SS）和铁基生物炭（Fe-Bio）对土壤pH、Eh、孔隙水中Cd和As动态变化及土壤Cd和As形态的影响，旨在筛选出可以同时钝化土壤Cd和As的潜在材料.结果表明，添加Sep、IMS、Sep-FM和SS材料提高土壤pH值，降低Eh值及土壤孔隙水中Cd的质量浓度；而且高剂量IMS（2.5%）和SS（5%）处理土壤孔隙水中As的质量浓度在整个培养期间均低于CK处理.然而添加Fe-Bio则使土壤pH降低和Eh值升高，且仅在湿润条件下降低溶液中Cd和As的质量浓度.所有供试材料均降低土壤可交换态Cd含量，提高可还原态、可氧化态和残渣态Cd含量.高剂量IMS（2.5%）、Sep-FM（2.5%）和SS（5%）处理还降低了土壤中可利用态As含量（非专性吸附态和专性吸附态As）、提高了晶形和非晶形铁铝氧化物结合态As的含量，而1% Fe-Bio处理则提高了土壤非专性吸附态、专性吸附态和残渣态As的含量.总之，高剂量的IMS、Sep-FM和SS能同时钝化土壤中Cd和As，促进其向生物难利用的形态转化，是修复Cd和As复合污染土壤的潜在材料.

Screening of Amendments for Simultaneous Cd and As Immobilization in Soil

Simultaneously reducing the availability of Cd and As is difficult owing to converse chemical behaviors of Cd and As in soil. In this study, amendments that can simultaneously immobilize Cd and As in soil were determined by an pure soil culture experiment in which flooding and wetting were performed for 30 d each. The effects of sepiolite (Sep), modified sepiolite (IMS and Sep-FM), steel slag (SS), and iron modified biochar (Fe-Bio) on soil pH, Eh, Cd, and As concentrations in pore water, and Cd and As fractions in soil were investigated. It showed that Sep (1%, 2.5%), IMS (1%, 2.5%), Sep-FM (1%, 2.5%), and SS (1%, 5%) treatments increased soil pH value and decreased Eh value and Cd concentrations in soil solution. In addition, As concentrations in soil solution treated with high doses of IMS (2.5%) and SS (5%) were lower than that of CK treatment during the whole incubation period. However, Fe-bio treatment decreased soil pH and increased Eh value and only decreased Cd and As concentrations in soil solution under wet conditions. Compared with the control, the application of the above amendments promoted the transformation of Cd fraction from exchangeable to reducible, oxidizable, and residual. High application rates of IMS (2.5%), Sep-FM (2.5%), and SS (5%) also reduced available As fraction (non-specifically sorbed and specifically-sorbed As fraction), and increased amorphous and poorly-crystalline hydrated Fe and Al oxide-bound As. On the contrary, Fe-bio treatment increased the fractions of non-specifically sorbed, specifically sorbed and residual As in soil. In short, IMS, Sep-FM, and SS are potential materials for remediation of Cd and As contaminated soil. They can effectively immobilize soil Cd and As and promote their transformation to the fractions that plants are difficult to uptake.