• 关键词：土壤溶液  化学形态  化学平衡模式  镉

• 基金项目：

• 熊礼明
• 中国科学院大气物理研究所,北京,100029

• 摘要：据土壤溶液的实际情况建立简便的平衡模式,研究了红壤、黄棕壤、黄潮土三种典型土壤溶液中Cd的化学形态和化学平衡.结果表明,溶液中Cd的主要形态为Cd²⁺、CdCl⁺和CdSO₄⁶.黄潮土还有一定量的CdHCO₃⁺,其它形态Cd很少,其中游离Cd²⁺占绝大部分.红壤最高,黄棕壤次之.红壤施石灰后游离Cd²⁺下降,CdSO₄⁶增加;添加氯化物后,溶液pH下降,大量Cd进入溶液中,CdCl⁺比例明显升高.溶液中Cd的形态分布与土壤Cd的生物有效性有一定关系.此外,溶解度图证明,供试土壤中不可能有Cd的矿物生成.Cd在固液相间的平衡受吸附解吸反应控制.

• Abstract：A simple chemical equilibrium model was developed to speciate Cd in soil solutions of red earth, yellow-brown earth and yellow fluro-aquic soil peviously amended with Cd. Results showed that Cd²⁺, CdCl⁺, and CdSO₄⁰ were the dominant species of Cd in soil solution. Limimg the red earth reduced free Cd²⁺ and increased CdSO₄⁰ in the species composition. Adding chlorides decreased soil pH and desorbed Cd from solid matrix, and CdCl⁺ and CdCl₂⁰rised dramatically. Solubility diagram suggested that the soil solution was far undersaturated with respect to all Cd minerals hence Cd activity in soil solution was controlled by sorption-desorption equilibrium of Cd between soil solid and solution phases.

• Key words：cadmium  chemical equilibrium model  soil solution  species

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