The Distribution And Magnetic Susceptibility Characteristic Of Heavy Metals Cu, Zn And Pb Of Urban Topsoils In Lanzhou

City is the central place for human social, economic, and cultural activities. Urban soil plays an important role in environment quantity for human residence and urban ecological function. However, human activities such as industrial activities, transportation have made heavy metal pollution of urban topsoils seriously. Therefore, studying heavy metal pollution of urban topsoil is practically significant. The urban topsoils in Lanzhou were taken to analyze their magnetic susceptibility, total contents and TCLP (Toxicity characteristic leaching procedure) extractable contents of heavy metals Cu, Zn, and Pb, in order to study the distribution of heavy metals Cu, Zn, and Pb and magnetic susceptibility characteristic of urban topsoils in Lanzhou. The results indicate that:The average contents of heavy metals Cu, Zn, and Pb of urban topsoils in Lanzhou are 39.64 mg/kg, 130.01 mg/kg, and 57.48 mg/kg, respectively. The contents of heavy metals Cu, Zn, and Pb are consistently higher than the background values of local soils. The urban topsoils in Lanzhou are contaminated by heavy metals Cu, Zn, and Pb to various extents.The average contents of heavy metal Cu of urban topsoils in Lanzhou in ranking are Xigu District > Chengguan District > Qilihe District > Anning District. The average contents of heavy metal Zn in ranking are Xigu District>Qilihe District> Anning District>Chengguan District. The average contents of heavy metal Pb in ranking are Chengguan District>Xigu District>Qilihe District>Anning District.All the individual pollution indexes of heavy metals Cu, Zn, and Pb of urban topsoils in Lanzhou are higher than 1, Pb pollution index is the highest, followed by Zn, and Cu is the lowest. All the integrated pollution indexes of heavy metals Cu, Zn, and Pb of urban topsoils in Lanzhou are higher than 3, which show that the urban topsoils in Lanzhou are seriously contaminated. The heavy metals pollution of urban topsoils in Xigu District is the most serious, followed by Chengguan District, and Qilihe District and Arming District are the lowest. The main causes of heavy metals pollution of urban topsoils in Lanzhou are industrial activities, transportation and commercial activities. All the heavy metals Cu, Zn, and Pb of urban topsoils in Lanzhou could be extracted by TCLP reagent. The average extractable contents of heavy metal Cu of urban topsoils in Lanzhou in ranking are Xigu District>Qilihe District>Chengguan District>Anning District. The average extractable contents of heavy metal Zn in ranking are Xigu District>Qilihe District>Anning District>Chengguan District. The average extractable contents of heavy metal Pb in ranking are Arming District> Chengguan District>Qilihe District>Xigu District.The magnetic susceptibility of urban soils are higher compared with those of natural soils. The magnetic susceptibility of urban topsoils are correlated with total contents and TCLP extractable contents of heavy metals Cu, Zn, and Pb, which implies that the magnetic susceptibility of urban topsoils could be indicated the pollution status of heavy metals Cu, Zn, and Pb of urban soil.