pH对镉在土水系统中的迁移和形态的影响

Effect of pH on transport and transformation of cadmium in soil water system

研究了４种红壤和水体系中ｐＨ对镉的迁移影响．结果表明：镉在土水体系中的迁移是一快反应过程，４种土壤对镉的吸附量随土水系统中ｐＨ的变化，可分为３个区域，即低吸附量区、中等吸附区，以及强吸附和沉淀区，在中等吸附区镉吸附量与ｐＨ呈正相关；ｐＨ６以下被吸附的镉中生物有效态镉量随ｐＨ的升高而增加，ｐＨ６以上被吸附的镉中生物有效态镉量随ｐＨ升高而降低．石灰导致镉毒性降低的主要原因是ｐＨ＞７５时镉主要以粘土矿物和氧化物结合态及残留态形式存在．

Effects of pH on transport and transformation of cadmium in soil water systems were studied. The results showed that the transport of cadmium in the soil water systems was a fast process.The variation in absorption capacity for cadmium with pH showed three distinct stages,i.e.,low adsorption stage at pH<ZPC,stable adsorption stage at ZPC<pH<6 0 and strong adsorption and precipitation stage at pH>6 0.Adsorption capacity for cadmium was positively correlated with pH at the stable adsorption stage.The bioavailability of adsorbed cadmium increased with pH when pH<6 while decreased with pH when pH>6. At pH value of 7 5,large perceentages of cadmium were bound to clays and oxides,reducing its toxicity.