Heavy air pollution happened twice in Shijiazhuang between March 1st and March 20th, 2016, as the heating period lasted and ended.The chemical compositions of the PM2.5 during the two heavy air pollution periods are analyzed with the help of SPAMS (single particle aerosol mass spectrometer).The causal factors of the heavy air pollution are then concluded from the comprehensive judgment and analysis of the PM2.5 mass concentrations and meteorological conditions.It turns out that the reason of the one-day heavy air pollution occurred during the heating period of March 2016 (from March 1st to March 15th) was the heavy accumulation of the particles produced by coal combustion (42.6%) and industrial processes (26.4%);the reason of the 3 d heavy air pollution occurred after the heating period of March 2016 (from March 16th to March 20th) was the heavy accumulation of the particles produced by vehicle exhaust (25.5%~25.9%) and industrial processes (23.0%~25.5%) in the earlier stage, and the heavy accumulation of the particles mainly produced by coal combustion(28.6%) and industrial processes(27.4%) in the later stage.In the whole air monitoring, it is proved that the correlation between PM2.5 and meteorological conditions was very strong: rHum/2.5=0.76,rPres/2.5=-0.58,rWd/2.5=-0.65,rTemp/2.5=0.35.In summary, in the humid, low-pressure, and stable weather condition, the particles produced by coal combustion and industrial processes could not be dissipated, but accumulated heavily and went through the secondary chemical reaction quickly and strongly, and then the heavy air pollution of March 4th happened.After the heating period, nearly in the same bad weather condition which the air pollutants cannot be dissipated, the particles produced by vehicle exhaust and industrial processes accumulated and went through the secondary chemical reaction quickly and strongly, and then the peak of pollution appeared on March 17th and 18th.Unlike the previous two days, it was the accumulation and secondary chemical reformation of particles from coal combustion and industrial processes that caused the heavy air pollution on the early morning of March 19th.%2016年3月1日~20日期间,石家庄市区于采暖期结束前后出现两次重污染天气.为探究重污染天气成因,利用位于石家庄市大气自动监测站(20 m)的单颗粒气溶胶质谱仪(SPAMS)对两次重污染天气期间的细颗粒物化学组成进行分析;并结合颗粒物质量浓度和气象条件等对重污染天气成因进行了推定.结果表明,3月采暖期(3月1日~15日)期间共发生为期1 d的重度污染天气,主要成因为来自燃煤(贡献率42.6%)和工业工艺源(26.4%)的颗粒物严重累积;采暖期结束后(3月16日~20日)出现了连续3 d的重度污染天气,前期主要成因为来自机动车尾气(25.5%~25.9%)和工业工艺源(23.0%~25.5%)的颗粒物严重累积;后期首要污染源变为燃煤(28.6%)和工业工艺(27.4%).监测过程中,PM2.5与气象条件的相关性较高,r湿度/2.5=0.76,r大气压/2.5=-0.58,r风速/2.5=-0.65,r温度/2.5=0.35.综合来看,高湿状态下空气的低压静稳和低空传输,共同促使燃煤及工业工艺源的颗粒物累积,二次转化加剧后导致3月4日的重污染天气;而采暖期结束后,在同样不利于扩散的气象条件下,机动车尾气及工业工艺源的颗粒物累积,二次转化加剧,从而导致3月17和18日污染小高峰;不同于前两日,燃煤和工业工艺源的累积,二次转化加剧,导致了3月19日凌晨的污染小高峰.
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