不同比例钙锌共存对土壤镉有效性的影响及其机制

Effect of coexistence of calcium and zinc at different ratios on the cadmium bioavailability in lateritic red soils and its mechanisms

采用盆栽试验,研究了赤红壤上两种镉污染水平下,施用不同比例钙锌对小油菜(Brassica Campetris,Lvar Conmuni)生物量、镉吸收量及土壤溶液中镉、钙、锌质量浓度的影响。结果表明,钙、锌以不同比例共存时并不会对赤红壤上小油菜的生长产生明显的影响;随着锌用量增加,土壤溶液中锌的质量浓度明显增加,土壤溶液中镉的质量浓度明显升高,小油菜体内镉含量明显降低;高镉污染赤红壤上,钙锌共存中钙用量增加,土壤溶液中钙的质量浓度明显增加。低、高镉污染赤红壤上,钙、锌共存摩尔比例为4∶1时,小油菜体内镉含量较对照平均分别降低34.2%和27.3%(两季平均值);而土壤溶液中镉的质量浓度较对照分别增加307%和120%。在低镉污染赤红壤上,锌施用量与小油菜体内镉含量呈显著负相关;高镉污染赤红壤上,锌施用量与土壤溶液中镉的质量浓度呈显著正相关。钙、锌以不同比例施入土壤时,锌施用量多少是控制土壤镉有效性高低的主要因素。

Pot experiments were conducted in two lateritic red soils with different Cd levels to investigate the effect of Ca/Zn applications at different ratios on the rape biomass, amounts of Cd uptake by rape, as well as Zn, Ca and Cd concentrations in lateritic red soil solutions. The results showed that the coexistence of Ca and Zn at different ratios did not exert significant effect on the rape growth. Increasing Zn ratio in the Ca/Zn application resulted in the elevated levels of Zn and Cd in soil solutions, while Cd concentrations in the rape decreased. In lateritic red soil with higher concentration of Cd, the Ca concentration in the soil solution increased with increasing Ca content in the Ca/Zn application. When the molar ratio of Ca/Zn was 4：1, compared with the control treatment, average Cd content in the rapes decreased by 34.2% and 27.3%, respectively in soils with low and high Cd levels, and Cd concentration in soil solution increased by 307% and 120%, respectively. Applied Zn amount was negatively correlated with Cd concentrations in rapes in soil with low Cd levels, whereas in soils with higher Cd levels, applied Zn amount was positively correlated to the Cd concentrations in soil solutions. It demonstrated that the amount of zinc applied to soils was the major factor that controlled Cd bioavailability when Ca and Zn were simultaneously applied to soils in various ratios.