2013-2015年合肥市PM2．5重污染特征研究

Characteristics of severe PM_(2.5) pollution in Hefei during 2013-2015

综合利用中国环境监测网公布的合肥市2013—2015年大气污染物浓度数据和合肥市气象站的常规气象资料,以及激光雷达探测资料、公益性行业(气象)专项(GYHY201206011)获得的气溶胶离子成分分析结果,分析了合肥市PM_(2.5)重污染(日均浓度>150μg/m3)特征。结果表明:(1)2013—2015年,合肥市PM_(2.5)浓度和重污染天数空间分布差异明显,东北部多、西南部少,1月各站差异最大。除了低浓度日(日均浓度≤35μg/m3),PM_(2.5)浓度都存在明显的日变化,午后低、早晚高,且随着污染程度加重,早上峰值出现时间推后。(2)重污染日臭氧以外的气态污染物浓度都显著上升。(3)重污染日常伴随着霾和轻雾天气,以稳定、小风天气为主,重污染日白天相对湿度偏高、风速偏小,600 m以下的消光系数显著增大且峰值高度降低。(4)重污染日PM_(2.5)中水溶性无机离子含量增高,其中NO_3^-含量的占比增加最多,超过了SO_4^(2-)的占比。

The air quality data published by the environmental authorities, the meteorological data collected at Hefei observato- ry during 2013- 2015, together with the vertical extinction coefficient data observed by lidar and water-soluble inorganic ions data of aerosols obtained during scientific field experiments were used to analyze characteristics of severe PM2.s pollution average PM2. 5 concentration ≥150 μg/ma） in Hefei. The results show that： （1） the PM2.5 pollution showed evident ern Hefei. Monthly variations of severe PM2.5 pollution days were similar at all sites wit January. The PM2.5 concentration showed an evident diurnal variation with two maxima in ly, and the morning maximum in severe pollution days often occurred later than in light po lution days, the concentrations of other gas pollutants except O3 increased obviously; （3） corresponded to haze and light fog, accompanied with light winds and stable stratification. poilu h the days largest difference o （daily spatial southwest ccurring in the morning and evening respective- lluted days; （2） in severe PM2.5 pol- severe PM2.5 pollution days usually The vertical extinction coefficients of aerosols below 600 m at the noon in severe pollution days were much higher than those in other days, while the occurrence height of maximum extinction coefficient decreased; （4） in severe pollution days, the water soluble inorganic ions in PM2.5 be came more abundant, and the percentage of NO3 increased most, exceeding the percentage of SO4^2- . The above results advance our understanding of the role of nitrate in the formation of high level PM2.5 and are helpful for the forecast and control of PM2.5 pollution.