The relationship between physicochemical characterization and the potential toxicity of fine particulates (PM2.5) in Shanghai atmosphere

Fine particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) was collected at urban and suburban sites in Shanghai from April 2005 to March 2006. Average mass concentrations of PM2.5 ranged from 43.5 to 149 μg m−3 in the urban area and 21.7 to 159 μg m−3 in suburban area. The mass levels of PM2.5 sampled at urban and suburban sites showed seasonal variation with much higher values in winter and spring, lower values in summer, and the lowest in autumn. The results of environmental scanning electron microscopy (ESEM) showed that Shanghai PM2.5 was consisted of soot aggregates, coal fly ashes, minerals, bio-particles and unidentified particles. Inductively coupled plasma atomic mission spectrum (ICP-AES) results showed total elements in Shanghai PM2.5 increased gradually from summer to winter and remained at a relatively high level in spring. There was a significant difference in the mass of elements in PM2.5 collected in urban and in suburban atmosphere. Enrichment factor (EF) analysis results demonstrated that K, Na, Ca, Mg, Al, Fe, Ba and Sr originated from natural sources, while As, Cu, Zn, Pb, Cd, Mn, Ni and Se were emitted from anthropogenic sources. The plasmid DNA assay showed that potential toxicity of Shanghai PM2.5 collected at urban and suburban sampling sites, and in different seasons, varied greatly. Toxicity of the Shanghai urban winter PM2.5 sample was much stronger compared to any of the other samples. Heavy metals in Shanghai PM2.5, including Cu, Zn, Pb, Cd, Cr, Mn, and Ni, might have synergic-effects on plasmid DNA damage.