还原稳定剂配伍对铬污染土壤的稳定化效果

Effect of reducing amendments combination on stabilization remediation of chromium contaminated soil

以某铬盐生产场地内的铬(Cr)污染土壤为研究对象,探讨了多硫化钙(CPS)、硫酸亚铁(FeSO_4)、零价铁粉(Fe^0)、葡萄糖和淀粉单用或复配对土壤中六价铬(Cr(Ⅵ))含量和浸出毒性的影响。结果表明:添加质量比3%的CPS和FeSO_4对土壤Cr(Ⅵ)的还原率分别为81.5%和46.4%,而Fe^0无显著还原作用,但FeSO_4和Fe^0对Cr(Ⅵ)的稳定效率分别为95.2%和90.9%,明显高于CPS(83.0%);养护5 d时,CPS+FeSO_4对土壤Cr(Ⅵ)的还原率和稳定效率分别为99.8%和97.0%,但养护30 d时,其还原率和稳定效率分别显著降低1.3和8.0个百分点;与CPS+FeSO_4类似,CPS+Fe^0对土壤Cr(Ⅵ)的还原率随养护时间增加而显著降低,但其稳定效率并未随养护时间增加而显著降低;此外,与CPS-6相比,Fe^0参与的复配处理对土壤总Cr和Cr(Ⅵ)的稳定效率显著增加,均达到99.8%以上,浸出浓度均小于0.05 mg·L^(-1);有机碳源参与的复配处理的还原率和稳定效率均随养护时间的增加而增加,其中CPS+Fe^0+葡萄糖处理养护30 d时土壤Cr(Ⅵ)为0.24 mg·kg^(-1),总Cr和Cr(Ⅵ)浸出浓度均小于0.05 mg·L-1,满足《重金属污染场地土壤修复标准》(DB 43 1165-2016-T)要求。同等药剂添加比例下,还原稳定剂复配可以取长补短,提高药剂对土壤Cr(Ⅵ)的还原率和稳定效率。

To investigate the stabilization of Cr（Ⅵ） in a contaminated soil, calcium polysulfide （CPS）, ferrous sulfate （FeSO4）, ferrous powder （Fe0）, glucose, amylum were applied alone or in combination and the concentrations of Cr（Ⅵ） in soil and leachate were tested. The reduction efficiency of Cr （VI） in soil after CPS and FeSO4 applied alone （at a rate of 3%） was 81.5% and 46.4%, respectively, while, limited reduction effect was observed after the application of Fe0. However, the stabilization efficiency of Cr （VI） for FeSO4 and Fe0 treated soils was 95.2% and 90.9%, respectively, and were both higher than CPS treated soil （83.0%）. The reduction and stabilization efficiency of Cr（Ⅵ） for CPS＋FeSO4 treated soil after cuing for 5 days were 99.8% and 97.0%, respectively, and were decreased by 1.3% and 8% after curing for 30 days, respectively. Similar decrease of reduction efficiency but changeless stabilization efficiency of Cr（Ⅵ） for CPS＋Fe0 treated soil during the 30 d curing period were observed. Compared with treatment CPS-6, the application of mixtures that contain Fe0 obviously enhanced the stabilization of total Cr and Cr（Ⅵ） in soil and their stabilization efficiencies were over 99.8% and the leaching concentration of Cr（Ⅵ） were lower than 0.05 mg·L^-1. Moreover, the reduction and stabilization efficiencies increased with the increase of curing time for the application of mixed amendments that contain organic materials. The concentration of Cr（Ⅵ） in soil was 0.24 mg·kg^-1 and concentrations of total Cr and Cr（Ⅵ） in leachate were lower than 0.05 mg·L^-1 after application of CPS＋Fe0＋glucose and curing for 30 d. Among the tested amendments, the reduction and stabilization effects of CPS＋Fe0＋glucose on Cr contaminated soil could meet the Standards for Soil Remediation of Heavy Metal Contaminated Sites （DB 43 1165-2016-T）. Under the same reagents application rate, the combination of reducing amendments showed complementary advantages and enhanced the reduction and stabilization effects on Cr（Ⅵ） in contaminated soil.