在铀尾渣污染土中壤添加磷对植物生长及积累重金属的影响

在重金属污染土壤中添加化学稳定剂，可降低重金属的生物有效性，阻控重金属进入食物链。设计盆栽试验，在铀尾渣污染土壤中添加不同浓度的磷肥(0、30、60、120、240和480 mg kg^-1)，调查磷对芥菜型油菜(Brassica juncea)和甘蓝型油菜(B. napus)的生长及植株积累重金属铀、镉、锌和铅含量的状况，分析添加磷肥前后植株内磷含量和土壤重金属DTPA提取态含量的变化。结果表明，添加磷肥前，铀尾渣污染土壤总氮、总磷、总钾和有机质的含量低，铀、镉、锌和铅的含量高，对两种油菜的生长有抑制作用；添加磷肥后，两种油菜体内磷含量增加，污染土壤中的铀、镉、锌和铅的DTPA提取态含量显著降低，其降幅分别为17.1%~70.5%、24.0%~57.6%、8.9%~32.4%和8.6%~55.8%；大幅度降低两种油菜体内的铀、镉、锌和铅含量，其含量与土壤中这些重金属DTPA提取态含量显著正相关；显著增加两种油菜的干重、株高、根长和叶绿素含量，显著降低其体内的SOD活性和MDA含量。因此在铀尾渣污染土壤中添加磷可有效减少重金属在油菜体内积累，降低重金属沿食物链传递的风险。

Effects of Phosphorus on Growth and Uptake of Heavy Metals in Plants Grown in the Soil Contaminated by Uranium Tailing

The uranium tailing contains uranium and other heavy metals like lead, cadmium and zinc, which usually makes the surrounding soil and water bodies seriously polluted with contaminated rain and dust. There is a potential threat to human’s health because the heavy metals can be absorbed and accumulated by the crops grown in the polluted areas, and then possibly transferred to human body by an environment-crop-food chain. The development of an economical and effective remediation method for the heavy-metal contaminated soil is urgent to improve environmental quality and enhance the food safety. As one of the fast-developing technologies, chemical stabilization has been widely studied, and the study on inhibition of heavy metal contamination by adding phosphorus-containing material to soil is becoming an international hotspot. In this study, two species of oilseed rapes, B. junea and B. napus, grown in containers with the uranium-tailing contaminated soil, were used to investigate the effects of phosphorus fertilization on plant growth and accumulation of heavy metals (U, Cd, Zn, and Pb). Container soil was treated by adding a phosphorus fertilizer NaH₂PO₄ with a rate of 0, 30, 60, 120, 240, and 480 mg P kg^-1, respectively. For the control soil (without adding phosphorus fertilization), there were a lower concentration of total nitrogen, phosphorus, potassium, and organic matter, and a higher concentration of U, Cd, Zn and Pb. Plant growth of both species was inhibited. Compared with the control group, the concentration of phosphorus significantly increased in plants grown in the P-fertilizer added soil. The DTPA-exactable concentrations of U, Cd, Zn, and Pb in this soil were decreased by 17.1–70.5%, 24.0–57.6%, 8.9–32.4%, and 8.6–55.8%, respectively. Also, addition of phosphorus in the uranium-tailing contaminated soil significantly decreased the contents of U, Cd, Zn, and Pb in plant organs. A significant positive correlation (P<0.01) was observed between the contents of U, Cd, Zn, and Pb in plant organs of both species and DTPA-exactable concentrations of these metals in the contaminated soil. Additionally, addition of phosphorus fertilization of 60-480 mg P kg^-1 significantly increased dry weight, height, root length and chlorophyll content of plants. A significant decrease of SOD activity and MDA content occurred in both species grown in the P-fertilizer treated soil compared to the control. Therefore, application of phosphorus fertilizer to the uranium-tailing contaminated soil is a practical and effective approach to reduce accumulation of heavy metals in plant organs of oilseed rapes and the risk of these pollutants entering the food chain.