煤矸充填复垦土壤可溶性镉的分布特征与运移模拟

在现场调查研究煤矸石充填复垦地上覆土壤可溶性镉含量的基础上,应用田间小区试验,模拟土壤可溶性镉的迁移特征。结果表明,土壤可溶性镉在时间和空间维度上都具有明显的分布特征:可溶性镉浓度沿剖面深度逐渐递增,即离煤矸石层越近,浓度越高;随时间推移,土壤下部接近煤矸石处,可溶性镉浓度的富集现象存在。模型模拟结果显示,由于土壤毛管力作用,接近煤矸石层的土壤可溶性镉浓度每年可增加10%左右,但表层土壤(0~40cm)增加速度缓慢或反而有所下降。尽管如此,由于植物根系活动,煤矸石中镉析出具有一定的生态环境风险。

Distribution and Transportion of Soluble Cadmium in the Reclaimed Soil Filled with Coal Wastes

Soluble cadmium in soil, including water soluble, exchangeable and part of the carbonate combination state, is capable of migrating into the solution under the condition of weak acidic to achieve the cadmium equilibrium between the solid and liquid phase. Its concentration can be used as one of the indicators of cadmium enrichment and transportion characterization in reclaimed soil filled with coal wastes. This paper simulated soluble cadmium transportion by convection -diffusion equation based on the investigation in -situ in reclaimed soil filled with coal wastes. And the field experiment was used to verify the reliability of the model through analyzing soil water characteristic parameters (e.g. soil water characteristic curves, unsaturated hydraulic conductivity). HYDRUS-1D program also was applied for the soluble cadmium migration characteristics in soil. The results showed that soil soluble cadmium distributions had the distinct characteristics with time and space dimensions. Soluble cadmium concentrations increased gradually along with the soil depth, namely the closer distance from coal waste layer, the higher concentration. And concentration enrichment of soluble cadmium consisted in the lower soil close to coal waste with process of time. The simulation results showed soluble cadmium concentration increases about 10% per year in soil close to coal waste layer owing to soil capillary force, but decreasing slowly in surface soi(l0~40 cm)or declining. Nevertheless, coal waste leaching will bring about the eco- logical environment risk of cadmium pollution because of the plant roots activities.