Heavy Metals Distribution, Magnetic Properties, Source Apportionment, and Potential Risks in Urban Street Dust of Northwest China

The enrichment levels, sources, and potential hazards of heavy metals (HMs) and magnetic minerals in street dust and sand-dust storm from an extremely arid city (Dunhuang) in the northwest of China were analyzed. The assessment was performed using pollution indices, magnetic parameters, positive matrix factorization (PMF), and risk assessment models. Average enrichment levels of HM (including Cd, Zn, Pb, Cu, Cr, Co, and Ni) in street dust were higher than those in urban topsoil and the background values. The enrichment factor, pollution load index (PLI), and geoaccumulation index showed that the HMs came from both natural and anthropogenic sources, with Cu, Zn, Pb, and Cd being strongly influenced by anthropogenic sources. The means mass-specific susceptibility (chi(lf)) and saturation isothermal remanent magnetization (SIRM) of street dust were 135.65 x 10(-8) m(3)/kg and 1792 x 10(-5)Am(2)/kg, respectively, indicating that the street dust continuously receives pollutants containing high levels of coarse pseudo single-domain and multidomain ferromagnetic minerals. Ni, Zn, Cd, Cr, Fe, and ferromagnetic particles were principally associated with the industrial source and accounted for about 30.4% of these HM contents. Pb and Co were mainly produced from coal mining and coal combustion sources. Cu was principally associated with traffic emissions. Al, Mn, and Co were mainly generated by natural sources, contributing 38.9%. The ecological risk of HMs in street dust was moderate with considerable risk in individual sites, driven by Cd. The non-carcinogenic risks of HMs were within safety limits, and the carcinogenic risks were below the receivable values.

Automated summary

This study analyzed the levels, sources, and hazards of heavy metals (HMs) and magnetic minerals in street dust and sand-dust storm from Dunhuang, an extremely arid city in northwest China. The results showed that HM enrichment levels in street dust were higher than in urban topsoil and background values, with both natural and anthropogenic sources. Magnetic parameters indicated the presence of pollutants containing coarse pseudo single-domain and multidomain ferromagnetic minerals. Industrial and traffic emissions were major sources of HMs, while coal mining and combustion contributed to the presence of Pb and Co. The ecological and non-carcinogenic risks of HMs were moderate, with Cd being the main driver of risk.