羟基磷灰石+沸石对稻田土壤中铅镉有效性及糙米中铅镉累积的影响

为研究组配改良剂羟基磷灰石+沸石(简称HZ)对稻田土壤Pb和Cd生物有效性以及糙米中Pb和Cd累积的影响,在湘南两矿区附近污染稻田中施用不同添加量(0、0.45、0.9、1.8 kg·m~(-2))的组配改良剂HZ,进行了水稻种植的田间试验。结果表明:与对照相比,当施用量为1.8 kg·m~(-2)时,土壤A中Pb和Cd的DTPA提取态含量分别降低69.6%和62.0%,TCLP提取态含量分别降低80.0%和41.8%,Mg Cl2提取态含量分别降低87.4%和19.4%;土壤B中Pb和Cd的DTPA提取态含量分别降低73.8%和82.7%,TCLP提取态含量分别降低65.8%和65.1%,Mg Cl2提取态含量分别降低99.8%和94.5%。施用0.45~1.8 kg·m~(-2)的HZ能使土壤A水稻糙米中Pb和Cd的含量分别降低36.4%~48.5%和4.9%~17.0%;土壤B水稻糙米中Pb和Cd的含量分别降低5.0%~41.3%和16.7%~20.2%。分析土壤p H和糙米中重金属含量与3种重金属提取态含量的关系得知,土壤p H增加是HZ降低土壤中Pb和Cd生物有效性的关键因素之一;比较得知,DTPA提取方法更合适表达重金属生物有效性,可用于糙米重金属含量的风险评估。

Effects of hydroxyapatite plus zeolite on bioavailability and rice bioaccumulation of Pb and Cd in soils

Hydroxyapatite and zeolite have been used to reduce bioavailability of heavy metals in soils. Here a plot experiment was designed to examine the effects of hydroxyapatite plus zeolite(HZ) on the bioavailability and brown rice bioaccumulation of Pb and Cd in two paddy soils near mining areas in southern Hunan, China. HZ was applied to the surface soil at rates of 0, 0.45, 0.9 kg·m^-2 and 1.8 kg·m^-2. Results indicated that:Compared with the control, applying 1.8 kg·m^-2 of HZ reduced soil extractable Pb by 69.6%, 80.0%, and 87.4% in Soil A, and 73.8%, 65.8%, and 99.8% in Soil B, respectively for DTPA, TCLP, and MgCl2, while DTPA, TCLP, and MgCl2-extractable Cd respectively decreased by 62.0%, 41.8%, and 19.4% in Soil A, and 82.7%, 65.1%, and 94.5% in Soil B. Adding HZ at 0.45~1.8 kg·m^-2 decreased Pb and Cd content in brown rice by 36.4%~48.5% and 4.9%~17.0% in Soil A and 5.0%~41.3% and 16.7%~20.2% in Soil B, respectively, as compared with the control. Correlation analysis showed that soil pH was one of key factors decreasing migration and bioavailability of Pb and Cd in soils after HZ applications. DTPA-extractable Pb and Cd were a better indicator of their bioavailability in soils.