镉污染稻田土壤土柱淋洗修复研究

摘要

以三氯化铁为淋洗剂,采用土柱淋洗法对镉污染稻田土壤进行了修复研究.系统考察了土壤的干湿状态、淋洗液浓度及体积、搅拌次数、淋洗时间等淋洗条件对Cd去除率的影响,深入探究了Cd在土柱中的分布规律.结果表明:“干洗”条件下的修复效果优于“湿洗”;淋洗液浓度、搅拌次数、淋洗时间及淋洗液体积的增加均能提升Cd的去除率,但提升程度有限;当采用“干洗”方式进行淋洗,且三氯化铁浓度为0.05 M、搅拌次数为3、淋洗时间为2d及淋洗液体积为450 mL时,Cd的去除率可达最大值25.4％;在此最优淋洗条件下,洗脱的Cd中有86.7％存在于孔隙水中.由此表明,在稻田淋洗修复过程中,高效排出孔隙水是修复的关键.%Remediation of cadmium-contaminated paddy soils by column leaching with ferric chloride was carried out.The effects of leaching conditions including dry or wet state of soil,concentration and volume of leaching solution,stirring times and leaching time on the removal rate of Cadmium (Cd) were investigated systematically.The distribution of Cd in the soil column was also studied in depth.Results suggest that the remediation effect of dry washing was better than that of wet washing.The increase of concentration and volume of leaching solution,and stirring times as well as leaching time could all result in a limited improvement of the removal rate of Cd.The removal rate of Cd achieved a maximum value of 25.4％ when using dry washing with the concentration of'leaching solution of 0.05 mol/L,three times of stirring,2 days of leaching,and 450 mL leaching solution.Under this optimal condition for leaching,nearly 86.7％ of the removed Cd existed in pore water,which implies that discharging the pore water efficiently is crucial in the process of leaching remediation for paddy soils.