2015年“九三阅兵”期间北京市空气质量分析

Analysis on air quality in Beijing during the military parade period in 2015

为研究区域性大气污染物减排措施对北京市空气质量的影响,结合地面观测的气象参数、常规污染物和PM_(2.5)化学组分,对"九三阅兵"期间北京市的空气质量进行分析.结果表明,阅兵期间北京市北风平均风速、温度、相对湿度和地面气压等气象要素水平与相邻时段相比较为接近,但北风频率偏高,整体大气扩散条件略有利.阅兵期间SO_2、NO_2、O_3、PM10和PM_(2.5)平均浓度分别为2.7、24.2、63.2、27.2和19.5μg/m^3,与相邻时段相比分别降低了26.0%、31.3%、24.5%、59.0%和59.4%;PM_(2.5)的降幅最大,体现了一次源排放和前体物排放同时减排的叠加作用.从PM_(2.5)化学组分来看,阅兵期间浓度最高前4位依次是OC(6.1μg/m^3)、NH_4^+(3.8μg/m^3)、SO_4^(2-)(3.4μg/m^3)和NO_3^-(2.5μg/m^3),OC中二次生成的组分仍高达57.6%.通过与相邻时段中相似天气形势下污染物浓度的对比测算了减排措施的"净环境效益",阅兵期间的减排措施使得SO_2、O_3、NO_2、PM_(10)和PM_(2.5)浓度分别降低了50.0%、0.7%、42.1%、45.7%和48.6%,并对APEC期间和阅兵期间O_3浓度变化不同的原因进行了讨论.

During the military parade period in2015,air quality in Beijing was analyzed to investigate the impact of regional-scale air pollutant control strategies on Beijing.Ground-observed meteorological data,regulated air pollutant concentrations,and chemical compositions of PM2.5were analyzed.The results showed that the average wind speed of north wind,temperature,relatively humidity and ground-level atmospheric pressure during the military parade period were at the same level with the adjacent period,whereas,frequency of north wind was obviously higher.In general,atmospheric dispersion conditions during the military parade period was more favorable than the adjacent period.The average concentrations of SO2,NO2,O3,PM10and PM2.5were2.7,24.2,63.2,27.2and19.5μg/m3,respectively,which decreased by26.0%,31.3%,24.5%,59.0%and59.4%compared with the adjacent period,respectively.The decrease of PM2.5was the largest,indicating the combination effect of reduction of primate emission and precursor emission.OC concentration(6.1μg/m3)was the highest in PM2.5chemical composition,followed by NH4+(3.8μg/m3)、SO42-(3.4μg/m3)and NO3-(2.5μg/m3).Notably,secondary OC accounted for57.6%of total OC even with the implementation of emission reduction measures.The net effectiveness of the emission reduction measures was calculated through comparisons of concentrations of air pollutants under similar meteorological conditions.Through the implementation of emission reduction measures,concentrations of SO2,O3,NO2,PM10,and PM2.5decreased by50.0%,0.7%,42.1%,45.7%and48.6%,respectively.In addition,the mechanisms of the different variations of O3during the APEC period and the military parade period were discussed.