不同磷酸盐对污染土壤中镉生物有效性的影响

采用盆栽试验,在镉二级和三级污染的红壤和褐土上添加不同磷酸盐（磷酸二氢铵、磷酸二氢钾、磷酸二氢钙）后种植小油菜40d,测定植株生物量、镉吸收量、土壤有效态镉含量、pH值,分析不同磷酸盐对污染土壤中镉生物有效性的影响。结果表明,3种磷酸盐使污染红壤和褐土上小油菜生物量分别提高了18.7%～291.1%和31.5%～991.2%,在红壤上提高顺序为磷酸二氢钙〉磷酸二氢钾〉磷酸二氢铵,而在褐土上则表现为磷酸二氢钙≈磷酸二氢钾〉磷酸二氢铵。3种磷酸盐影响下小油菜吸收镉量,在镉二级污染水平的红壤上表现为显著提高8.3%～60.6%,而在镉三级污染水平的红壤上则表现为显著降低了4.6%～58.4%。污染红壤有效态镉含量在加入3种磷酸盐后提高了17.0%～122.7%,提高顺序为磷酸二氢钙〉磷酸二氢钾〉磷酸二氢铵;而磷酸二氢铵使污染褐土有效态镉含量降低了2.4%～13.4%。3种磷酸盐使红壤pH值提高了0.24～0.99。可见,不同土壤类型、不同镉污染水平下,3种磷酸盐对土壤镉的生物有效性的影响存在差异,其机制有待进一步研究。

Effect of Different Phosphate on Bio-availability of Cadmium in Contaminated Soils

Pot experiment was implied to study the effects of the three kinds of phosphate（NH4H2PO4,KH2PO4,Ca（H2PO4）2） on the Cd bioavailability in polluted red and cinnamon soil with the second and third pollution standard level of Cd.After rapeseed grew for 40 d in the pots,we analyzed the above-ground biomass and Cd uptake by rapeseed,soil available Cd,and soil pH.Results showed that the rapeseed biomass in polluted red soil and cinnamon soil increased by 18.7%～291.1% and 31.5%～991.2% respectively.The order of the increment in biomass by phosphates in the red soil was：Ca（H2PO4）2KH2PO4NH4H2PO4,while the order was：Ca（H2PO4）2≈KH2PO4NH4H2PO4 for the cinnamon soil.The uptake amount of Cd in rapeseed increased by 8.3%~60.6% significantly in the red soil with the second pollution standard level of Cd.However,the uptake amount of Cd in rapeseed decreased by 4.6%～58.4% significantly in the red soil with the third pollution standard level of Cd.The adding of phosphates increased soil available Cd content by 17.0%～122.7% in polluted red soil.The order of increment in soil available Cd by phosphates was：Ca（H2PO4）2KH2PO4NH4H2PO4.However,the available Cd content was decreased by 2.4%～13.4% after adding NH4H2PO4 in polluted cinnamon soil.Additionally,the pH value in the polluted red soil was increased by 0.24～0.99 after adding three kinds of phosphate.In conclusion,the different effects of accompanied cations of various phosphates on Cd availability contributed greatly to bio-availability of Cd in polluted soils and further study are supposed to illustrate the mechanism.