Grain-size distribution and contamination characteristics of heavy metal in street dust of Baotou, China

The concentration, contamination level and grain-size distribution of Ba, Co, Cr, Cu, Mn, Ni, Pb, V and Zn in street dust samples from Baotou, an industrial city in the semi-arid area of northwest China, were determined in the present work. Contamination levels of heavy metals were assessed based on the pollution load index (PLI) and geo-accumulation index (I-geo). The results for the measured concentrations indicated that street dust in Baotou had elevated heavy metal concentrations, particularly Ba, Co, Cr and Pb. The concentrations for these metals (Ba, Co, Cr and Pb) lay in the ranges of 1.2-4.7, 4.0-10.7, 1.7-5.8 and 1.2-8.7 times the background values of local soil, respectively. Except for the Ba and Co, all of the analyzed heavy metals in the dusts were largely accumulated in the <50 lm particles. Results for the I-geo assessment indicated that Co, Cr, Pb, Ba and Zn showed different degrees of contamination of the street dust. Mn, Ni and V in the dust samples fell in the category of `uncontaminated'. The PLI results showed that most dust samples were 'uncontaminated to moderately contaminated' by heavy metals.