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

ABSTRACT This study investigated the pollution characteristics and chemical composition of PM2.5 from Jan. 13-24, 2018 during a long-lasting winter haze episode. The average daily concentrations of PM2.5, water-soluble inorganic ions, organic carbon (OC), elemental carbon (EC), and trace elements were 169.29±56.98, 111.45±44.62, 20.74±6.79, 6.48±1.79 and 10.53±3.84 μg m-3, respectively. The OC/EC ratios indicated a mixed contribution of intensive traffic emissions and secondary formations. The estimated primary organic carbon (POC) and secondary organic carbon (SOC) concentrations increased as the pollution levels increased. POC dominated the OC when there was mild and moderate pollution; SOC dominated the OC when there was severe pollution. The enrichment factor (EF) and geo-accumulation index (Igeo) were used to assess the contamination level of PM2.5-bound metal(loid)s, revealing a strong positive correlation. A health risk assessment was conducted to evaluate the non-carcinogenic and carcinogenic risks of PM2.5-bound metal(loid)s on human health. The metal(loid)s As, Cr, Pb, and Sb may pose a potential non-carcinogenic risk for both children and adults. The metal(loid)s As and Pb may also pose a potential carcinogenic risk. The total non-carcinogenic and carcinogenic risks for PM2.5-bound metal(loid)s were slightly higher for adults (3.07×103, 3.78×10-3) compared to children (2.71×103, 2.99×10-3). These levels did not depend on the pollution levels, but rather the concentrations of PM2.5-bound metal(loid)s. The public and government should implement effective measures to mitigate health risks created by PM2.5-bound metal(loid)s during winter haze episodes in Xiangyang, central China.