改性椰壳炭钝化修复农田土壤镉、铅的长期稳定化效果及生态风险评估

为探究改性椰壳炭钝化修复土壤中镉、铅的长期效果及生态风险,采取硝酸-高锰酸钾改性方法优化椰壳炭表征,通过设置不同改性椰壳炭用量,探究其对土壤中镉、铅生物有效性的长期影响,结合土壤-农产品综合质量影响指数评价结果,最终验证其场地应用的可行性。结果表明:改性椰壳炭可显著提高土壤镉、铅的稳定性,当用量>20 g/kg时,钝化培养12周,土壤中镉、铅以残渣态为主,固定率较对照组分别提高了8%~23%和11%~24%。钝化培养15~18周,土壤镉、铅有效态含量均低于安全阈值,且种植蔬菜未检测到重金属超标,不存在生态风险。采用改性椰壳炭进行土壤重金属场地修复具有一定应用价值。

LONG-TERM STABILIZATION EFFECT AND ECOLOGICAL RISK ASSESSMENT OF SOIL CADMIUM AND LEAD BY USING MODIFIED COCONUT SHELL BIOCHAR

Heavy metal pollution in farmland soil attracted broad attention in China due to its harm to human health and ecological environment. In order to explore the feasibility of biochar on remediating soil heavy metals in pilot-scale, the long-term stabilization effect and ecological risk of soil cadmium and lead was studied by using the nitric acid and potassium permanganate modified coconut shell biochar. With application of different dosages of biochar, the long-term variation of soil cadmium and lead bioavailability was discussed, in combination with the results of soil-agricultural product comprehensive quality impact index, to evaluate the possible ecological risk after the remediation. The results showed that the modified biochar could significantly improve the stability of soil cadmium and lead. When the applied amount of modified bichar was higher than 20 g/kg, soil cadmium and lead were mainly in residual fraction after 12 weeks and the immobilization rates were increased by 8%~23% and 11%~24%, respectively, compared with the control group. After 15~18 weeks’ remediation, the contents of bioavailable cadmium and lead in soil were maintained within the safety threshold, and no excessive metals were detected in the planted vegetables. This study indicated that it might be desirable to use modified coconut shell biochar for large-scale remediation of soil heavy metals.