Pollution Characteristic and Bio-availablity of Heavy Metals in Soils and Plants from a Typical Industrial District in Lanzhou

Soil and plant samples were collected in typical industrial district in Lanzhou,Gansu Province. The levels,spatial distribution and potential ecological risk of heavy metals were investigated. In the surface soils collected from typical industrial district,the mean concentrations of lead(Pb),chromium(Cr),zinc(Zn),copper(Cu) and cadmium(Cd) were 113.25,92.15, 78.63, 44.31 and 0.32 mg/kg respectively. The concentrations of individual heavy metal were higher than the background value and the concentrations of heavy metals in topsoil showed a trend in an order of Pb Cr Zn Cu Cd.Moreover,the concentration of heavy metals decreased with the depth of soil. Through description of spatial variation of heavy metals in different areas,industrial activities and transports were the important sources of heavy metal pollution in soil in the study area. The geo-accumulation index(Igeo)was adapted to evaluate the pollution status and the soil quality contaminated by heavy metals in the study area. Results showed that the soil was moderately polluted by Cu,Zn,Pb and Cr,but the soil was severely polluted by Cd. The available contents of heavy metals in soils showed that Zn,Cd and Cu element were easy to accumulate from soil to plant,but Pb and Cr element were hard to be uptaken by plants. The analytical results showed that higher Zn contents were detected in plants,and the enrichment ability of heavy metals in plants from high to low was ZnCuCrPb.