[Characteristics of Haze Pollution Episodes During Autumn and Winter in 2018 in Shijiazhuang].

The mass concentration and chemical composition of fine particles were continuously observed on-line from October 31 to December 3, 2018 at Hebei Key Laboratory of Haze Pollution Prevention and Control in Shijiazhuang. The characteristics of haze pollution in autumn and winter in Shijiazhuang were analyzed. The results showed that during the observation period, four haze pollution episodes occurred with PM as the primary pollutant, and the maximum daily concentration was 154, 228, 379, and 223 μg·m, respectively, reaching a heavy pollution level or above. The main components of PMwere water-soluble inorganic ions (WSⅡ) and carbon-containing aerosols, accounting for (60.7±15.6)% and (21.6±9.7)% of PM mass concentration, respectively. Compared with clean days, the mass concentration of WSⅡ and carbon aerosol during haze pollution increased by 4.4 times and 3.1 times, respectively, which was the main cause of haze pollution. NO, SO, and NH(SNA) were the main components of WSⅡ, accounting for (91.5±17.3)% of the total WSⅡ concentration, of which NO took up the highest proportion. The explosive growth of SNA during haze pollution was the main reason for the extremely high PMconcentration. Under non-high humidity conditions, the formation rates of unit mass substrates (NO, SO) were not significantly different, but the transformation of SO was significantly promoted after the liquid phase oxidation of SO was triggered under high humidity conditions. The atmosphere in Shijiazhuang is rich in NH, and the molar ratio of (NH) to (NO+2×SO) in PM was greater than 1. The presence of a large amount of NH could promote the transformation of NO and SO and aggravate pollution. During the haze pollution period, the accumulation of primary pollutants from coal and motor vehicles was the main reason for the increase in carbon-containing aerosol. Compared with clean days, the formation of SOC was inhibited. Before the beginning of the warm season, the mobile form was the main pollution source of PM, contributing 30.8% and 39.8% of PM mass concentration. With the increase of coal combustion emissions, the contribution of coal-fired sources gradually increased to 25.5%, becoming the primary pollution source.