Pollution Characterization, Source Identification, and Health Risks of Atmospheric-Particle-Bound Heavy Metals in PM10 and PM2.5 at Multiple Sites in an Emerging Megacity in the Central Region of China

A total of 588 daily PM filters were collected at five sites in Zhengzhou, and the mass concentrations and sources of the elements were analyzed. The health risks and source regions of the particles and toxic elements were also estimated. The results indicated severe PM2.5 and PM10 pollution, especially at traffic sites. Additionally, the PM10-bound As far exceeded the Chinese standards. Although the total elemental levels were relatively low at the rural site, they were high at the GY site. High levels of crustal elements were also observed at the SSQ and HKG sites. Seasonal-variation analysis revealed that the crustal elements, more abundant in the PM10, occurred at high levels in spring; the combustion-source elements, more abundant in the PM2.5, caused significant pollution in winter; and the elemental concentrations were low in summer. The coefficients of divergence for the PM2.5 were slightly higher than those for the PM10. Vehicles, industry, coal combustion, oil fuel, dust, and biomass burning were important sources of the PM-bound elements. Although the ZM site was characterized by low traffic and high contributions from biomass burning and dust emission, the HKG site featured a high proportion of emissions from traffic sources, and the SSQ site was also highly affected by vehicular pollution. Whereas elements in the PM2.5 largely originated in combustion sources, those in the PM10 received greater contributions from dust sources. The levels of As and Ni posed intolerable carcinogenic risks (CR) and, along with that of Pb, also demonstrated significant non-CR risks. Children were more sensitive than adults to these risks, and the daily intake pathway demonstrated the highest CR and hazard index (HI) values. Obvious differences in the CR and HI values were detected between the various sites, suggesting the necessity of multiple-site studies for health risk assessment. Jiyuan, Jiaozuo, Xuchang, and Zhoukou; Pingdingshan and Nanyang; and Jiyuan, Jiaozuo, Xinxiang, Anyang, and Kaifeng were the main potential sources of PM2.5, PM10, and As, respectively.