Spatial distribution, environmental risk and source of heavy metals in street dust from an industrial city in semi-arid area of China

Environmental risks associated with Co, Cr, Cu, Mn, Ni, Pb, V and Zn in street dust collected from Baotou, a medium-sized industrial city in a semi-arid area of northwest China, were assessed by using enrichment factor and the potential ecological index. Their spatial distributions and sources in the dust were analyzed on the basis of geostatistical methods and multivariate statistical analysis, respectively. The results indicate that street dust in Baotou has elevated heavy metal concentrations, especially of Co, Cr, Cu, Pb and Zn. Co in the dust was significantly enriched. Cr and Pb were from moderate to significant enrichment. Cu and Zn were from minimal to moderate enrichment, whereas Mn, Ni and V in the dust were from deficient to minimal enrichment. The ecological risk levels of Co and Pb in the dust were moderate to considerable and low to moderate, respectively, whereas those of other heavy metals studied in the dust presented low ecological risk. Different distribution patterns were found among the analyzed heavy metals. Three main sources of these heavy metals were identified. Cr, Mn, Ni and V originated from nature and industrial activities. Cu, Pb and Zn derived mainly from traffic sources, and Co was mainly from construction sources.