外源Cd在不同类型土壤中的稳定化特征

Stabilization Characteristics of Exogenous Cd in Different Types of Soil

为明晰镉(Cd)在不同类型土壤中的稳定化特征和有效性差异,以四川省6种主要的农耕土壤酸性紫色土、中性紫色土、石灰性紫色土、灰潮土、典型黄壤和漂洗黄壤为研究对象,通过土壤培养试验,对外源Cd进入土壤后的稳定化时间、化学形态和有效Cd含量进行了对比分析,进一步结合盆栽试验下各土壤中小白菜生物量和Cd含量,探讨了外源Cd在6种土壤中的化学行为和污染效应.结果表明:(1)6种土壤的有效Cd含量在外源Cd添加后的15 d内迅速降低,后趋于平稳.稳定后,漂洗黄壤和酸性紫色土的有效Cd含量显著高于其他4种土壤,石灰性紫色土最低(1.01 mg·kg^(-1));(2)6种土壤中的Cd均以可交换态的占比最高(42.51%~56.07%),其次,漂洗黄壤和典型黄壤中的铁锰氧化物结合态Cd,石灰性紫色土中的碳酸盐结合态和灰潮土中的有机络合态Cd的占比相对较高;(3)低含量Cd处理下(0.5 mg·kg^(-1)),6种土壤中小白菜的生长均无明显抑制,生物量与对照无显著差异,但可食部位Cd含量却有不同程度地富集,表现为典型黄壤和漂洗黄壤显著高于其他4种土壤;高含量Cd处理下(2 mg·kg^(-1)),6种土壤中小白菜的生长均受到明显抑制,小白菜Cd含量和土壤有效Cd含量均以石灰性紫色土最低,酸性土壤尤其是漂洗黄壤最高.

To clarify the characteristics of stabilization and availability of exogenous cadmium(Cd)in different types of soils,six main agricultural soils in Sichuan province,including acidic purple soil,neutral purple soil,calcareous purple soil,gray fluvo-aquic soil,typical yellow soil,and rinsed yellow soil,were used in this study.A soil culture experiment was conducted to explore the differences in stabilization time,chemical form,and effective Cd content between the six types of soils.Additionally,the effects of exogenous Cd on the growth and Cd accumulation of cabbage growing in different soils was discussed.The results showed the following:(1)with exogenous Cd treatment,the available Cd content of the six soils decreased sharply within 15 d after Cd addition and then tended to be flat.After 30 d,there was no significant difference.The available Cd contents of rinsed yellow soil and acidic purple soil were significantly higher than that of the other four soils,and the content of calcareous purple soil was significantly lower(1.01 mg·kg^(-1)).(2)After stabilization,exchangeable Cd was the main Cd form in the six soils,up to 42.51%-56.07%.The relative proportions of other Cd forms differed greatly between different soils.The proportion of iron and manganese oxides in the rinsed yellow soil and typical yellow soil was higher,whereas organic complex Cd,residual Cd,and carbonate-bound Cd were higher in the gray fluvo-aquic soil,neutral purple soil,and calcareous purple soil,respectively.(3)The characteristics of availability and bioavailability of Cd among different soils were significantly different with different exogenous Cd doses.With the lowest Cd dose(0.5 mg·kg^(-1)),compared with that in the control,there was no significant decrease in Cd content in the edible parts of the cabbage,but Cd accumulation in the edible parts differed.The Cd contents of edible parts of the cabbage growing in typical yellow soil and rinsed yellow soil were significantly higher than that of the other soils.With the highest Cd dose(2.0 mg·kg^(-1)),the growths of cabbage growing in all six soils were significantly inhibited.The available Cd contents of rinsed yellow soil and acidic purple soil were significantly higher than that of the other four soils,which is consistent with the Cd content in the edible parts of the cabbage.The available Cd contents and the Cd content in the edible parts of the cabbage in calcareous purple soil were the lowest,and acidic soils,especially in rinsed yellow soil,had the highest.