Quantifying the pollution characteristics of chemical components in PM2.5 in the North China Plain, China: Spatiotemporal variation and health risk

Abstract

To fully grasp the features of aerosol chemical composition in North China Plain (NCP) region from winter through spring, this study chose five typical cities (Jinan, Shijiazhuang, Taiyuan, Tianjin and Zhengzhou) and analyzed their spatiotemporal variation, sources and health risk from January to March 2018. The average mass concentration of PM2.5 ranged from 65.65 μg/m3 (Tianjin)–101.23 μg/m3 (Shijiazhuang). It was high in the southwest and low in the northeast because of better diffusion conditions in coastal areas than inland. In PM2.5, organic carbon (OC) accounted for 8.28% (Jinan)–35.36% (Shijiazhuang), elemental carbon (EC) accounted for 3.75% (Tianjin)–13.31% (Shijiazhuang), water-soluble ions (WSIs) accounted for 34.8% (Shijiazhuang)–57.16% (Tianjin), and elements accounted for 3.01% (Zhengzhou)–4.74% (Taiyuan). In carbonaceous aerosols, primary OC (POC) was dominant in coastal areas while secondary OC (SOC) was dominant inland. The source of OC and EC emissions in northern and central cities was coal combustion, whereas in southern cities, both vehicles and coal combustion were involved. Although NO3−, SO42− and NH4+ accounted for 70.09% (Taiyuan)–73.02% (Jinan) of WSIs over the whole region, SO42− dominated in the west and center region, and NO3− dominated in the east and south. K, Fe, and Ca had the highest concentrations in elements, accounting for 76.77% (Tianjin)–79.80% (Taiyuan). Potential ecological risk index (RI) for 7 toxic heavy metal elements—Cd, Cr, Cu, Ni, Pb, V and Zn—more than 600 (Pb contributed 51.37%) in Taiyuan and more than 1200 (Cd contributed 87.54%–97.71%) in other cities showed severe metal pollution. Kids and adults living here faced non-carcinogenic risk by exposure pathways of dermal contact and respiratory inhalation, respectively. At the same time, kids also faced non-carcinogenic risk.