Characteristics and health risks assessment of PM-bound heavy metals during winter in urban areas of northern China: A case study in Kaifeng.

The health impact of heavy metals in atmospheric PM has garnered increasingly widespread attention. We have collected PM samples in a typical city (Kaifeng) within the Central Plains Urban Agglomeration in China during winter and measured the mass concentration of PM-bound heavy metals. The pollution of As and Cr in the urban atmosphere requires significant attention. As PM concentrations increased, the enrichment factors (EFs) of Mn, Cu, Zn, As, and Pb also rose, suggesting a growing contribution from anthropogenic emissions. The analysis showed that the hazard quotient (HQ) for the non-heating and heating periods (HQ < 1) did not result in a cumulative non-carcinogenic health risk to humans. Regarding carcinogenic effects, As and Cr exhibit significant carcinogenic impacts on both children and adults (ELCR>1 × 10), indicating that the carcinogenic risks posed by As and Cr under PM exposure in Kaifeng could not be overlooked. It was found that industrial and biomass combustion are the primary sources of carcinogenic risk in Kaifeng city. From the non-heating to the heating period, the industrial carcinogenic risk increased from 37.12 % to 43.39 %, while the contribution of biomass burning remained at 25 %. This result was strongly correlated with the high proportions of heavy metal elements such as As, Mn, Pb, and Ni from the metal refinery industry. The results of this study revealed the equally important source of heavy metals, compared to coal combustion in North China Plain. In addition to residential coal combustion, industrial emissions are a major source of PM-bound heavy metals in Kaifeng, contributing significantly to overall air pollution and providing a useful reference to mitigating human health risks in the area.