Spatial Distribution and Assessment of Heavy Metals in Surface Soil,Jiayuguan City,Gansu Province

Key words: 
• soil heavy metal /
• principal component analysis /
• Nemero index /
• geoaccumulation index /
• Jiayuguan city

Abstract: Jiayuguan, located in the northern Qilian Mountains, is a new steel industry and tourism city in NW China at the transportation junction of the ancient Silk Road. To measure the concentration of heavy metals in the surface soil of Jiayuguan city and evaluate their concentration and determine the sources of heavy metal pollution, the amounts of six heavy metal elements (Cr, Cd, Cu, Pb, Ni, Zn)in 134 surface soil samples were determined by inductively coupled plasma mass spectrometer (ICP-MS). The average concentrations were:Cr 281.6 mg/kg; Cd 0.35 mg/kg; Cu 60.68 mg/kg; Pb 51.39 mg/kg; Zn 108.65 mg/kg; and Ni 161.0 mg/kg. Their concentration in the soil was evaluated by the Nemero comprehensive index (P_N)and the geoaccumulation index (I_geo). The pollution levels of the geoaccumulation index were in the order of Cr > Cd > Pb > Cu > Zn > Ni. The overall heavy metal pollution levels in each functional area was industrial area > gobi area > living area > agricultural area. The concentration of heavy metal elements (except Ni)in the gobi area were higher than those in agricultural areas. In addition to industrial factors, the absence of surface vegetation aggravated the enrichment of heavy metal elements. The possible sources of pollution of each element were analyzed by principal component analysis, combined with the spatial distribution of concentration, Nemero index and the geoaccumulation index. Cr and Zn are mainly industrial products of steel production and processing. Traffic is the source of Cd, Cu and Pb. The sources of Ni are possibly related to the steel industry of background value.