Status Of Heavy Metals In Vagetable-soil Systems In Foshan City And Its Control

The status of four heavy metals(Cd, Pb, Zn, and Cu) in vegetable soils in Foshan City was investigated. The results show that the concentration of each investigated heavy metal in the soils was greater than the mean level of the metal obtained based on either Guangdong Province wide or China wide soil survey. Of these metals, Cd was the primary contaminant. In addtion to soils, concentrations of Cd in vegetables grown in the investigated soils were also investigated. The Cd concentration in the vegetables far exceeded the national standard. It was found that the concentrationof Cd in green vegetables was very significantly correlated with the concentration of either exchangeable Cd, or oxide-bound Cd or total Cd.The paper also investigated the effect of red mud (Bauxsol) on the heavy metal polluted soil. The result indicated that the sole cadmium treatment with relative lower concentration (20mg/kg) could promote the growth of Ipomoea aquatica. Under the condition with several heavy metal elements polluted soil, the growth of Ipomoea aquatica was inhibited, and the content of Cd in vegetables were also larger than the control. The higer the concentration of cadmium was added into the soil, the worse the plant grew, the lower the plant biomass was and the higher the concentration of cadmium was accumulated in the plant. The application of red mud could abate the influence of heavy metal elements on the growth of Ipomoea aquatica and reduce the accumulation of cadmium in the plant. Red mud also could regulate the soil pH value.