[Characteristics and Formation Mechanism of a Multi-Day Haze in the Winter of Shijiazhuang Using a Single Particle Aerosol Mass Spectrometer (SPAMS)].

A multi-day haze episode occurred in Shijiazhuang during November 18-26, 2014. The characteristics were studied based on the data collected by the single particle aerosol mass spectrometer (SPAMS) located in the automatic monitoring station (20 meters) of Shijiazhuang. In accordance with the source spectral library of atmospheric pollutant emissions in Shijiazhuang, the main sources were distinguished and analyzed. The mass concentration of particulate matters and meteorological conditions being taken in account, the causes of haze in winter were also studied. It turned out that fine particulate matters in the Shijiazhuang air were mainly from 7 different sources: the tracer ion of coal source was Al; the tracer ions of industry sources were OC, Fe, and Pb; the tracer ion of motor vehicle tail gas source was EC; the tracer ions of dust source were Al, Ca and Si; the tracer ions of biomass burning source were K and levoglucosan; the tracer ions of pure secondary inorganic source were SO4-, NO2-, and NO3-, and the tracer ion of dining source was HOC. Of the above mentioned, OC, HOC, EC, HEC, ECOC, rich potassium particles minerals and heavy metals were 8 dominant polluting groups in hazy days. OC and ECOC particles were the majority, which accounted for more than 50% and 20% of the overall measured particles. OC particles were mainly discharged from coal combustion and industrial processes, and ECOC particles were mainly from coal combustion and vehicle exhaust emissions. When haze occurred in Shijiazhuang the proportion of pollutant particles of NH4+, SO4- , NO2- and NO3- increased, of which NH4+ was the most sharply increased. The mixed degree between EC, OC and NH4+, So4-, NO3- in the haze was higher than usual, of which NH4+ was the most sharply increased. In the static and stable weather gaseous (SO2, NO(x), NH3, VOCs) pollutants and particles were difficult to spread and accumulated rapidly, which were discharged from coal combustion, the process of the medical industry and the automobile exhaust. The gaseous pollutants tended to react for the second time and formed the ammonium nitrate and ammonium sulfate particles. Secondary particles were formed by collision and mixed with each other adequately or mildly, which caused the reduction of atmospheric visibility. This was the main cause for the haze during the winter in Shijiazhuang.