化学淋洗与生物质炭稳定化联合修复镉污染土壤

Chemical leaching combined with biochar stabilization remediate cadmium contaminated soil

为探讨土壤淋洗与生物质炭稳定化联合修复技术对镉(Cd)污染黄棕壤修复效果的影响,研究通过振荡淋洗实验、BCR连续化学提取法和CaCl_2一次提取法,筛选确定污染土壤的最佳淋洗方案,并比较了淋洗修复、淋洗+稳定化修复技术对污染土壤中Cd生物有效性的影响。结果表明:3种淋洗剂的淋洗效率强弱顺序为EDTA-2Na>HCl>柠檬酸,最佳淋洗条件为0.12 mol·L^(-1)EDTA-2Na在固-液比1:4条件下振荡淋洗3 h,Cd的洗脱率为81.3%;淋洗后土壤中Cd的有效态(F1+F2)百分比减少了51.0%,显著降低了污染土壤的重金属总量及其环境风险;相比于单一淋洗修复技术,EDTA-2Na在添加体积(V_(添加))为最佳淋洗体积(V_(最优))的80%时,淋洗后再加入3%玉米秸秆炭稳定化15 d的联合修复技术能够将土壤中有效态Cd含量(CaCl_2-Cd)从8.13 mg·kg^(-1)降低到0.42 mg·kg^(-1)。因此,淋洗修复后施加玉米秸秆炭的联合修复技术,能够有效降低重金属污染土壤的生态环境风险,提高土壤环境质量。

In order to identify the influence of soil leaching method combined with the biochar stabilization on cadmium （Cd） contaminated yellow-brown soil remediation, the soil leaching experiments, the method of BCR sequential chemical extraction and the one-step extraction by CaCl2 were performed to select out the best solution for soil leaching. After that, the efficiency of chemical washing on soil Cd bioavailability was compared with the combined technique of soil leaching and the biochar stabilization. Results showed that the washing efficiency of three eluent agents is listed in turn as EDTA-2Na〉HCl〉citric acid. The best leaching method is under the condition of 0.12 mol·L-1 EDTA-2Na, the soil-liquid ratio of 1 ： 4, and 3 h of vibration leaching. The Cd extraction ration is nearly 81.3%. After washing, the percentage of available Cd in soil reduced by 51.0%. 1Thus the leaching method significantly decreased the soil total heavy metal contents and their environmental risk in soil. Compared with the leaching remediation method solely, we used the method of EDTA-2Na leaching （Vaddition/Voptimal = 80%） combined with 3% corn-straw biochar （15 d stabilization） for soil Cd remediation. We reduced the soil available Cd contents （CaCl2-Cd） from 8.13 mg·kg-1to 0.42 mg·kg-1. In conclusion, the combination of soil leaching method with biochar stabilization is effective in reducing the ecological environment risk of heavy metal contaminated soil, and is useful in improving the soil quality.