| Specificity of heavy metals pollution index of greenhouse vegetable soils in Lanzhou city was studied for the potential ecological risk. The potential ecological risk was used to assess the ecological hazards of heavy metals in greenhouse vegetable soils. The results showed that the average concentration of Cd, Pb, Cr, Hg and As were higher than the local background soil value with different planting years. With the increase of planting years, the test heavy metals contents in the soil profiles all had increasing trend, and the contents were obviously higher in facility vegetable fields. The potential ecological risks results of these heavy metals showed that,compared to the National Soil Quality Standard(Grade Ⅱ) evaluation standard, the E¹and RI value of five heavy metals were all less than 40 and 150, posing little ecological hazard. If the local background soil value was used as evaluation standard, with different planting years Cd and Hg were at a higher level that posing Grade域hazard. The five kinds of heavy metals comprehensive potential ecological risk index (RI) was 157.73 in equal or greater than 10-year planting soil, that posing the secondary hazard. In addition, their RI value
closed to the secondary hazards in less than or equal to 5-year and 6~9 years planting years of soil. |
