场地土壤稳定化后有效态砷的浸出及影响因素

Leaching Effect of Available Arsenic in Site Contaminated Soil by Stabilization

对2种不同砷含量的场地土壤进行稳定化处理,并用4种不同浸提方法对稳定前后有效态砷进行浸出,效果评估结果显示:稳定前后有效态砷浸出率为连续提取法(SEP)】EPA毒性浸出法(TCLP)】国标硫酸-硝酸法(SNP)】合成浸出沉降法(SPLP)。三价砷浸出率的变化趋势与总有效态砷一致。连续提取方法能较好地提取土壤中具有迁移能力的有效态的三价砷。价砷的稳定效果非常显著,稳定后的浸出率较稳定前下降了40%左右。当浸出液pH在2.88~6区间时,随pH增大,三价砷和总有效砷的浸出率减小;pH在6~9区间,随pH增大,三价砷和有效砷浸出浓度增大。当pH为6时,土壤中有效态砷最稳定,不易迁移。三价有效态砷的浸出效果与体系中阴离子含量密切相关,SO42-和NO3-的抑制性较强。

Stabilization was implemented for two kinds of Arsenic-contaminated soil with different concentration levels.Four kinds of extraction methods of toxicity assessment were tested, and the results showed that the leaching efficiency of available arsenic is: SEP>TCLP>SNP>SPLP. The stabilization is obvious for arsenite, and the leaching efficiency decreased by 40% before stabilization. The trend of arsenite is corresponding to that of the available arsenic. SEP is a good method to extract the available arsenic in soil, and identify the soluble part of arsenic in soil. When pH in 2.88~6, total leaching concentration of available arsenic decreased with the increase of pH; pH in 7~9, leaching concentration of available arsenic increased with the increase of pH; available arsenic was the most immobile when the pH was 6. After the stabilization treatment, the three valent arsenic in soils and concentration of available arsenic significantly decreased,the the stabilizing effect was significant. The leaching effect is related to the anion level, such as the strong suppression ability of SO42-and NO3-.