2015年12月北京市一次重污染过程中PM_(2.5)特征分析

2015年入冬以来京津冀区域重污染频发,综合分析了2015年12月19—26日京津冀及周边地区发生的一次重污染过程中PM_(2.5)分布特征及成因。监测数据显示,2015年12月北京市重污染日共计13 d,累计月均值为151.8μg/m3。在12月19—26日一次重污染过程中,区域污染面积均超过40万km2,北京市单站PM_(2.5)小时均值超过800μg/m3。污染初期北京市南部地区PM_(2.5)浓度明显偏高,且PM_(2.5)极端高值出现在南部站点。污染输送阶段,北京市PM_(2.5)小时浓度在短时内呈爆发式增长,浓度增值是年均值的2~5倍。污染缓解阶段,偏北风作用,浓度明显下降。除了极端不利的天气形势外,区域散煤排放是造成重污染的重要原因;河北省唐山、保定、廊坊、石家庄等城市区域输送加重了污染程度。

ANALYSIS ON THE CHARACTERISTICS OF PM2.5 IN A HEAVY AIR POLLUTION EPISODE IN BEIJING IN DECEMBER 2015

During the winter of 2015,regional heavy air pollution episodes occurred frequently.The paper comprehensively analyzed PM2.5 characteristics and formation causes of a heavy air pollution episode during 19th ～ 26th in December 2015.Results showed that a total of 13 heavily polluted days existed in December in Beijing with the cumulative monthly average concentration of 151.8 μ g/m3.During this episode,regional pollution areas were more than 400 thousand square kilometers and hourly averaged concentration of PM2.5 was more than 800 μg/m3 among 35 sites in Beijing.In the early period of air pollution,the concentration of PM2.5 was significantly higher in the southern area of Beijing,and the extreme high values of PM2.5 tended to occur in the southern part of Beijing.In the air pollution transport phase,concentrations of PM2.5 were in an explosive growth in the short term with the added value 2 ～ 5 times of that of the annual averaged.In the pollution alleviating stage,concentrations of PM2.5 were significantly decreased by northerly winds.In addition to extreme adverse weather conditions,residential coal emissions was an important cause of heavy air pollution and regional transport from Tangshan,Baoding,Langfang,Shijiazhuang and other cities affected Beijing significantly.