植物吸取修复及钝化处理对后茬水稻镉吸收的影响

摘要

采集湖南湘潭县某地镉(Cd)污染酸性农田土壤及其经伴矿景天分别吸取修复两季和三季后的土壤,采用盆栽试验研究了经伴矿景天修复及钝化改良与否对土壤pH、有效态Cd、Zn以及水稻生长和稻米Cd、Zn浓度的影响.结果表明:未改良的处理,随着修复次数的增加,土壤pH显著降低,降低幅度为0.26~0.38个单位;且修复两季、三季土壤CaCl2提取态Cd浓度较未修复土壤分别降低19.4%、24.0%;修复后土壤种植水稻品种W184,其糙米中Cd浓度显著降低,但依然超标;修复三季土壤种植低积累水稻品种IRA7190,其糙米中Cd由0.47 mg/kg降为0.03 mg/kg.施加钝化剂海泡石和石灰(10 g/kg+1 g/kg)后,修复两季、三季土壤的pH显著升高,较未施钝化剂处理土壤pH分别提高0.95、0.72;土壤CaCl2提取态Cd浓度分别降低79.8%、79.5%;修复两季、三季土壤上水稻W184糙米的Cd浓度与未施加钝化剂相比,分别降低27.3%、44.4%,均降至国家食品安全限值0.2 mg/kg以下;无论是否添加钝化剂,伴矿景天吸取修复三季的土壤上水稻IRA7190糙米中Cd浓度均仅0.03 mg/kg.%A pot experiment was carried out to study the effects of phytoextracation bySedum plumbizincicola and stabilization on soil pH, extractable cadmium (Cd) and zinc (Zn) concentrations in soils, and on rice (Oryza sativa L.) growth, uptake of Cd and Zn in a heavy metal contaminated acidic soil. Paddy soils after different phytoextraction times were collected from Xiangtan County of Hunan Province. The results showed that after two and three times of phytoextraction, soil pH decreased by 0.26 and 0.38 units and soil CaCl2-extractable Cd concentration reduced by 19.4% and 24.0%, respectively, compared with unphytoextracted treatment. After phytoextraction, Cd concentration in the brown rice of variety W184 reduced significantly, but still exceeded the national standard of China. Cadmium concentration in brown rice of variety IRA7190 was 0.03 mg/kg in phytoextracted soil, which met the requirement of safety production. After applying sepiolite and lime (10 g/kg + 1 g/kg), soil pH increased by 0.95 and 0.72, soil CaCl2-extractable Cd concentration decreased by 79.8% and 79.5% and Cd concentration in brown rice of variety W184 decreased by 27.3% and 44.4% in the soils after two or three times of phytoextraction, respectively. Whether it was added stabilizer or not, Cd concentration in brown rice of variety IRA7190 was only 0.03 mg/kg when grown on soil phytoextracted three times.