北京空气重污染红色预警期间污染物与气象因子特征

揭示空气重污染红色预警期间污染物与气象因子的变化特征对空气质量预报和污染减排措施评估具有重要参考价值。利用大气污染和气象观测资料，研究了北京2015年11-12月空气重污染红色预警时期污染物浓度、气候特征及气象因子对空气质量影响。结果表明，PM2.5在大气颗粒物中占有较大比重，为首要空气污染物；在重污染峰值时段，城郊PM2.5与PM10比值（R）相差不大，可达0.9以上，空气呈均匀混合的高PM2.5浓度特征，而空气质量较好时城区R值明显高于郊区；研究时段气候特征与历史同期相比有明显差异，其中平均风速偏小19%，平均气温偏高0.23 ℃，气温日较差减小，而多次小型降水增加了空气湿度，导致相对湿度值偏高40%，垂直方向上的逆温层或等温层则加剧了空气重污染的形成和发展，重污染过程中的红色预警措施明显降低了颗粒物浓度；风速与污染物浓度呈指数相关，城郊风速分别低于2.0和2.5 m·s-1时，空气质量较差、污染物浓度随风速升高快速下降，而当城郊风速大于2.0和2.5 m·s-1时变化特征则相反；相对湿度与污染物浓度呈幂相关，相对湿度在65%左右为空气质量特征发生变化的转折点；由于气温日较差存在季节变化，其与空气质量相关关系不太显著。

Beijing pollutants and meteorological factors characteristic during red alert periods of air heavy pollution

It has important references in the air quality forecasting and measures assessment of emissions reduction for revealing pollutants and meteorological factors change characteristic during red alert periods. This paper using atmospheric pollution and meteorology data to research the Beijing pollutants concentration, climate characteristics and the impact of meteorology factors on air quality during the red alert periods of air heavy pollution in November-December 2015, the results showed that:PM2.5 was the primary air pollutant, which accounted for a large proportion in atmospheric particulate matters. The ratio (R) of PM2.5 and PM10 was slight difference in urban and suburban during heavy pollution peak periods, which could up to more than 0.9, and the air was characterized as PM2.5 uniformly mixing and high concentration;while the R was higher significantly in urban than in suburbs when the air quality was better. The climate characteristics were great differences compared with the historical period, in which the averaged wind speed was lower 19%, averaged temperature was higher 0.23℃, and the daily temperature range was reduced evidently. Meanwhile, air relative humidity increased by 40% due to little rains of many times. Temperature inversion layer and isothermal layer in vertical exacerbated the formation and development of air heavy pollution, and the red alert measures reduced the particulate matters concentration significantly in heavy pollution process. Wind speed and pollutants concentration was exponential correlation, when the wind speed less than 2.0 and 2.5 m·s-1 respectively in urban and suburban regions, the air quality was worse and the pollutants concentration decreased rapidly with the wind speed increasing, while the variation characteristic was on the contrary as the wind speed was greater than the above values. Relative humidity and pollutants concentration was power exponent correlation, 65% was an obvious break point for air quality change characteristic. The relation between daily temperature range and air quality wasn't significant due to its seasonal changes.