2种组配改良剂对稻田土壤重金属有效性的效果

为研究2种组配改良剂LS(碳酸钙+海泡石)和HZ(羟基磷灰石+沸石)对土壤重金属的生物有效性以及水稻吸收累积重金属的影响,在湘南某矿区附近污染稻田中施用了不同添加量(0,2,4,8g/kg)的两种组配改良剂,并进行了水稻种植的田间试验.结果表明,施用2~8g/kg组配改良剂LS和HZ均能使土壤pH值和CEC含量显著增加,有机质含量变化不明显,LS比HZ更能提高土壤pH值和CEC含量.施用2~8g/kg组配改良剂LS能使土壤中Pb、Cd、Cu和Zn的TCLP提取态含量分别降低25.7%~52.2%、12.7%~25.7%、6.4%~17.2%和8.6%~23.4%,施用2~8g/kg HZ使土壤中Pb、Cd、Cu和Zn的TCLP提取态含量分别降低57.6%~80.1%、7.0%~40.9%、2.3%~22.7%和4.5%~33.2%.两种组配改良剂能显著降低土壤中Pb、Cd、Cu和Zn的生物有效性,抑制水稻植株对Pb和Cd的吸收,土壤Pb、Cd和Cu的TCLP提取态含量与水稻根系和糙米中Pb、Cd和Cu的含量之间存在显著或极显著的正相关关系,TCLP提取态含量能较好的表示重金属在土壤中的生物有效性.

Effects of two combined amendments on heavy metal bioaccumulation in paddy soil

Stabilization of heavy metals in situ was investigated. Two combined amendments (LS, limestone + sepiolite; HZ, hydroxyhistidine + zeolite) were applied to paddy soil with multi-metal (Pb, Cd, Cu, and Zn) contamination at ratios of 0.2%, 0.4%, and 0.8% (w/w). The effects of these two combined amendments on heavy metal bioavailability in soil, and on uptake and accumulation of heavy metals in rice plants were investigated. The experiment results indicated that application of LS and HZ significantly increased soil pH values and cation exchange capacity contents, while the organic matter contents did not change obviously. Higher soil pH values and CEC contents were observed with LS treatment soils than HZ. Application LS and HZ resulted in a reduction in toxicity characteristic leaching procedure (TCLP) extract metal contents of amended soils. Compared with the control soil, contents of Pb, Cd, Cu, and Zn in TCLP extracts were decreased by 25.7%~52.2%, 12.7%~25.7%, 6.4%~17.2%, and 8.6%~23.4%, respectively, as a result of 0.2% to 0.8% addition of LS and decreased by 57.6%~80.1%, 7.0%~40.9%, 2.3%~22.7%, and 4.5%~33.2%, respectively, as a result of 0.2% to 0.8% addition of HZ. LS and HZ significantly decreased the bioavailability of Pb, Cd, Cu, and Zn in the paddy soils, and inhibited the bioaccumulation of heavy metals in rice organs, resulting in decreasing the concentrations of Pb, Cd, and Cu of rice roots, shoots, husks, and brown rice. Significant positive linear correlations were found between heavy metal concentrations in TCLP extracts and those in rice tissues (roots and brown rice) except for Zn. Extracting heavy metals with TCLP was a suitable method for estimating heavy metal bioavailability concentrations of amended soil.