Urban street dust bound 24 potentially toxic metal/metalloids (PTMs) from Xining valley-city, NW China: Spatial occurrences, sources and health risks.

Street dusts (SDs) were a significant tracer to understand the pollution status of potentially toxic metal/metalloids (PTMs) in local environment. In this study, a total of 157 SDs were collected in the valley-city of Xining, NW China, with the objective to systematically investigate the spatial occurrences, sources and health risk status of 24 PTMs bound in SDs. The basic datasets of pH and size-fractions showed that the SDs with PTMs were more alkaline and dominated with the coarse particle sizes between PM10-50, respectively. Results of concentration levels and spatial status of 24 PTMs processed with multi-statistical tools well established the sources identification in monitored local areas. It was suggested that the principal elements, Al, Fe, Si, K, Ca, Na, Mg, coupled with the trace elements Bi, Ga, Nb, Ni, Rb, Sr, Th, U, Y, Zr, As, Mn, Ti, V, Ce and La would be possiblely predominated by geogenic source or nature material, whereas contamination of Ba, Cu, Pb and Zn was clearly related to traffic-related sources. Peculiar associations among Cr and Co were possiblely enriched in SDs very close to the alloy industries. However, Sb and Sn differed from other observed PTMs, which appeared to derive predominantly from the coal combustion other than sources of electronic and mechanical industries. Compared to the integrated potential ecological risk index (PERI) of all PTMs with considerable contamination level and ecological risk, the single PTM of Sb posed very high risk. Calculated Hazard Index (HI) suggested ingestion as the most important exposure pathway for the majority of PTMs in children and adults, and no significant health risks of non-carcinogenic to children and adults were found except Cr (2.78) exposured to children. However, the evaluated cancerous risk was in the acceptable range both to children and adults except for the case of Cr exposure to adults (1.55E-06) compared to other PTMs. Although the carcinogenic risk was found no significant level, the maps of spatial carcinogenic risks above the threshold for children and adults were observed in some local monitoring areas, which should be attention and not to be always ignored.