黏土矿物原位修复镉污染稻田及其对土壤氮磷和酶活性的影响

分别以黏土矿物坡缕石和海泡石作为钝化材料,对重金属镉污染的酸性水稻土壤进行原位钝化修复田间示范试验,考察了两种黏土矿物在不同添加剂量下对稻谷产量、糙米镉含量及土壤中有效态镉含量等变化的影响,用以表征修复效果.同时,深入研究了两种黏土矿物对土壤pH、土壤水解氮、有效磷含量及相关酶活性的影响以表征其对土壤环境质量的影响,并对各项理化指标之间的相关性进行分析.结果表明,田间示范条件下两种黏土均提高了土壤pH,降低了土壤中镉的生物有效性,明显降低了糙米中镉含量.其中,经2.00 kg·m-2坡缕石和2.25 kg·m-2海泡石处理后,糙米镉含量最大降幅分别为54.6%和73.5%,分别降低至0.32和0.18 mg·kg-1.土壤过氧化氢酶、脲酶、酸性磷酸酶及蔗糖酶的活性均得到不同程度的提高,表明经钝化修复后土壤中相关代谢反应得到恢复;两种黏土矿物对土壤中水解氮含量无明显影响,但降低了土壤有效磷含量.综合总体表现,两种黏土矿物可被推荐作为镉污染酸性稻田土壤的原位钝化修复材料.

In-situ remediation of Cd-polluted paddy soil by clay minerals and their effects on nitrogen, phosphorus and enzymatic activities

In-situ immobilization field demonstration of Cd-polluted paddy soil by palygorskite and sepiolite was conducted to investigate the immobilization effects according to a set of variables (grain yields and Cd concentration in brown rice; soil available Cd content, pH, hydrolyzable nitrogen, available phosphorus and soil enzymatic activities). Results showed that the application of palygorskite and sepiolite could increase soil pH, reduce the bioavailability of Cd in soil and Cd concentration in brown rice. The addition of palygorskite (2.00 kg·m^-2) and sepiolite (2.25 kg·m^-2) significantly decreased Cd accumulation in brown rice by contents of 54.6% and 73.5%, and Cd contents in brown rice were reduced to 0.32 and 0.18 mg·kg^-1, respectively. The changes in soil enzymatic activities proved that certain metabolic recovery occurred after immobilization. Palygorskite and sepiolite had no obvious effects on hydrolyzable nitrogen contents, but reduced soil available phosphorus contents. According to the overall performance, palygorskite and sepiolite can be applied as immobilization agents for Cd polluted acid paddy soil.