A Long-lasting Winter Haze Episode in Xiangyang, Central China: Pollution Characteristics, Chemical Composition, and Health Risk Assessment

This study investigated the characteristics and chemical composition of PM2.5 during a long-lasting winter haze episode (Jan. 13-24, 2018) in Xiangyang of central China. The average daily concentration of the PM2.5 equaled 169.29 +/- 56.98 mu g m(-3), with water-soluble inorganic ions (WSIIs), organic carbon (OC), elemental carbon (EC), and trace elements accounting for 111.45 +/- 44.62, 20.74 +/- 6.79, 6.48 +/- 1.79, and 10.53 +/- 3.84 mu g m(-3), respectively. The OC/EC ratios indicated mixed contributions from intensive traffic emission and secondary formation, and the estimated concentrations for the primary organic carbon (POC) and the secondary organic carbon (SOC) increased with the level of pollution. POC dominated the OC during mild and moderate pollution, whereas SOC dominated it during severe pollution. A strong positive correlation was found between the enrichment factor (EF) and geo-accumulation index (IGeo) values, which were used to assess the contamination level of PM2.5-bound metal(loid)s. A health risk assessment, which was conducted to examine the non carcinogenic and carcinogenic risks of the PM2.5-bound metal(loid)s, found that As, Cr, Pb, and Sb posed potential non carcinogenic risks to both children and adults and that two of these elements, As and Pb, also posed potential carcinogenic risks. The total non-carcinogenic and carcinogenic risks from the PM2.5-bound metal(loid)s were slightly higher for adults (3.07 x 10(3) and 3.78 x 10(-3)) than children (2.71 x 10(3) and 2.99 x 10(-3)) and depended on the concentrations of the metal(loid)s rather than the level of pollution. Thus, the public and the government should implement appropriate measures to mitigate the health risks posed by PM2.5-bound metal(loid)s during winter haze episodes in Xiangyang.