Variations of PM2.5 Mass Concentration at Chaoyang Site in Beijing During 2013-2016
Using the PM2.5 mass concentration and surface wind data from February 2013 to January 2016 at Chaoyang Environmental Meteorological Station in Beijing, the characteristics of PM2.5 and its influence by surface wind are analyzed. The results show that the annual concentration of PM2.5 is 80.6±4.0 μg·m-3, 2.3 times the annual concentration limits (35 μg·m-3) regulated in the ambient air quality standard (GB3095-2012) of China. Its seasonal variation is obvious with the highest concentration in winter (115.1 μg·m-3) and the lowest in summer (58.5 μg·m-3). The dominant wind direction at Chaoyang Site in Beijing is ENE-E-ESE, and the wind speed ranges between 0.2-2.0 m·s-1. The concentration is the highest (109.1 μg·m-3) in the dominant ENE-E-ESE wind direction and the lowest (39.5 μg·m-3) in WNW-NW-NNW. With the increase of wind speed, PM2.5 concentration increases first and then decreases. The highest concentration (139.2 μg·m-3) appears at the wind speed of 0.4 m·s-1. When the wind speed is in 0.2-2.0 m·s-1, the concentration is mainly affected by ENE-E-ESE, and when the wind speed is 2-6 m·s-1, the value is influenced by ESE more. By comparing with the PM2.5 data from other sites, we found that the different characteristics of pollution sources and ground winds result in the difference of PM2.5 mass concentration in different wind directions.