Comparative major components and health risks of toxic elements and polycyclic aromatic hydrocarbons of PM 2.5 in winter and summer in Zhengzhou: Based on three-year data

In this study, 102 PM2.5 samples were collected from an urban site in Zhengzhou during winter and summer from 2012 to 2015. The meteorological impact, chemical characteristics, and health risks of the toxic elements and polycyclic aromatic hydrocarbons (PAHs) in PM2.5 were compared between the two seasons. PM2.5 pollution was relatively severe, especially in winter when meteorological conditions exhibited critical influence on PM2.5 concentration. NO3−, SO42−, and NH4+ were the three most abundant species, accounting for 79% and 90% of total measured water-soluble inorganic ions in winter and summer, respectively. OC, EC, and SOC exhibited relatively high concentrations in winter, and SOC contributed >40% in OC in both seasons. The seasonality of PAHs was associated with PM2.5, with high contribution of four-ringed and five- to six-ringed PAHs in winter and summer, respectively. Fe, Al, Zn, Mg, Mn, and Pb were the most abundant elements in PM2.5 in both seasons. The levels of V, Ag, and As in the winter were almost 8.3, 6.2, and 2.7 times higher than those in summer, respectively. The cancer risk values of As, Ni, and Pb were all higher than 10−6 for adults and children in winter and summer. The non-carcinogenic risks of Pb, As, and Sb for children were beyond the safe level, especially from ingestion. PAHs, BaA, BaP, BbF, and DaA showed potential carcinogenic risk. BaA, BaP, and BbF showed higher cancer risk in winter than in summer for adults and children, whereas DaA showed higher cancer risk in summer than in winter. The calculated non-carcinogenic risk of BaP for children in winter was beyond the safe level. BAP caused high health risk for adults through inhalation but through ingestion and dermal contact for children.