[Heavy metal content in street dust and environmental risk assessment of agricultural city: A case study of Xuchang City].

The characteristic of heavy metals in street dust is an effective means to evaluate the quality of the urban environment. The content and spatial distribution of heavy metals in street dust of Xuchang City was analyzed. The geo-accumulation pollution index and potential ecological risk index were used to assess the environmental risks of heavy metals in street dust. The results showed that the mean concentration of Cu, Pb, Zn, Cr, Ni, Co, Mn and As was 25.4, 41.9, 145.3, 96.7, 18.5, 9.0, 408.1 and 7.8 microg.0g1-, respectively. Concentrations of Ni, Co, Mn and As were lower than the background values in soil of Henan Province. Cu, Pb, Zn and Cr concentrations were 1.80, 2. 14, 2.42 and 1.52 times as high as the background values, indicating their enrichment in street dust. Except for Co, Mn and As, the spatial distribution of Cu, Pb, Zn, Cr and Ni showed a decreasing trend from the northwest to the southeast, reflecting differences of urban function zoning and human activity intensity. The assessment results of geo-accumulation pollution index showed that Ni, Co, Mn and As were at pollution-free level, while the pollution of Cu, Pb, Zn and Cr was mild, with pollution levels in descending order: Zn > Pb > Cu > Cr. The potential ecological risk index was 40.71, belonging to low level of ecological risk.