不同钝化剂和培养时间对Cd污染土壤中可交换态Cd的影响

原位化学钝化技术是修复重金属污染土壤的重要途径之一，通过施入一些钝化剂以降低土壤中重金属有效态含量，从而减少其迁移及对植物的毒害。选取羟基磷灰石（HA）、磷矿粉（PRX和PRH）、沸石、赤泥、新鲜植物残体、玉米秸秆粉末以及相应的处理共21种钝化剂，在同一培养条件和添加浓度下，比较其对人工Cd污染土壤中可交换态Cd含量的影响，并分析了其在不同培养时间对钝化效果的时间效应，试验的结果对于筛选Cd污染土壤钝化剂有着重要的意义。结果表明，纳米化赤泥、羟基磷灰石和纳米化酸洗赤泥可显著降低土壤中可交换态Cd含量，钝化比例高达35%-55%；赤泥、酸洗赤泥、沸石达15%-25%；富含巯基植物蒜苗、油菜、大葱植物残体也可达20%-25%。磷矿粉、大葱粉末、玉米秸秆和巯基化玉米秸秆的钝化效果相对较差；HA、铵型沸石、纳米赤泥、酸洗纳米赤泥、干油菜粉末、酸洗赤泥对可交换态Cd的钝化效果的时间效应不明显；赤泥、大葱残体、特别是玉米秸秆和巯基玉米秸秆随时间增长钝化效果增加显著，在8周和16周时段钝化效果较好。

Effects of Different Amendments and Incubation Times on Exchangeable Cadmium in Contaminated Soils

In-situ immobilization of heavy metals by adding extraneous amendments in contaminated soils has been identified as a cost-effective measure for soil remediation. The immobilizing amendments could decrease the concentrations of available heavy metals, and thus effectively decrease their mobility, toxicity/bioavailability in soils. In the present study, hydroxyapatite （HA）, phosphate rock powder（PRH and PRX ）, zeolite, red mud, plant offal, and their modified products were applied to the Cd-contaminated soils to assess the efficiency of these materials in immobilization of soil Cd. After incubation for different times, the concentration of exchangeable Cd was determined. The results showed that the concentration of exchangeable Cd in soils was decreased using red mud nanoparticles and HA by 35%-55%, using red mud, acid-treated red mud, and zeolite by 15%-25%, and using the sulphydryl（-SH） containing materials including garlic leaf, scallion, rape offal by 20%-25%. The immobilization by PRX, PRH, scallion powder, maize straw and sulfhydrylated maize straw were less effective compared with the above materials. The immobilizing effects of HA, ammonium saturated zeolite, red mud nanoparticles, and acid- treated red mud were stable at different incubation times, while the immobilizing effects of red mud, scallion offal, maize straw and its sulfhydrylation dispose increased along with the incubation times, especially for maize straw and its sulfhydrylated materials after eight weeks or longer incubation time. The results in the present study might be of practical importance in screening of amendments for remediation of soils contaminated with cadmium.