春节期间北京地区交通出行规律对热岛效应和大气污染的影响

利用北京地区2006—2015年春节及其前后三周的城区、郊区站数据分析了早晚高峰期出行活动对城市热岛效应、NO_x浓度、PM_2.5浓度的影响。结果表明人口、交通、社会活动的密集程度的确会对城市热岛效应和大气污染物浓度造成一定的影响:(1)第-3、-2、+2、+3周(以下称"BG时段")与春节周(以下称"CNY时段")间的城市热岛效应差异在早高峰期间平均为0.30℃,在晚高峰期间平均为0.43℃,在其他时段平均为0.26℃,晚高峰对城市热岛效应的影响更明显;(2)BG时段与CNY时段城、郊NO_x浓度差的最大差异出现在08时,为54.95μg/L。在早高峰期间为48.55μg/L,晚高峰期间为23.44μg/L。城市晚高峰出行活动对NO_x浓度城、郊差异的贡献量随着夜间的不利扩散条件而延迟出现峰值,城市早高峰出行对NO_x浓度城、郊差异的增大作用更为突出;(3)城郊PM_2.5浓度BG时段高于CNY时段的时间出现在05—19时,早高峰期间平均差值为12.82μg/m³,晚高峰期间平均差值为8.22μg/m³。考虑到汽车尾气中的超细粒子和污染气体需要在空气中进行化学反应或者吸湿增长才能变成PM_2.5,因此PM_2.5浓度的变化情况并不完全对应于早晚高峰出行的时间,而是有所延迟。

The impact of morning peak and evening peak of traffic on differences of heat island effect and air pollution in Beijing

The urban heat island effect,NOxand PM2.5 concentration between urban and suburban stations have been analyzed to figure out the effects of morning peak and evening peak on them in Beijing,based on the data of the urban and suburban stations during CNY and BG 2006—2015.The results indicate that the intensity of population,transportation and social activities affect urban heat island and air pollutants.(1)The difference of urban heat island effect between BG and CNY is 0.30℃in the morning peak period,0.43℃in the evening peak period and 0.26℃in the other time.The influence of the evening peak on urban heat island effect is more obvious.(2)The maximum NOx concentration difference between urban and suburban stations in BG and CNY appears at 08:00,which is 54.95μg/L.And it is 48.55μg/L in the morning peak and 23.44μg/L in the evening peak.The contribution of urban late peak travel activities in the evening peak to the NOxdifference between urban and suburban stations is delayed with the adverse diffusion at night.And the role in the morning peak is more prominent.(3)The PM2.5 concentration difference between urban and suburban stations in BG and CNY is positive from 05:00 to 19:00,which is 12.82μg/m3 in the morning peak and 8.22μg/m3 in the evening peak.Considering that the ultra-fine particles and polluting gases in automobile exhaust need to undergo chemical reaction or hygroscopic growth in the air in order to become PM2.5,the change of PM2.5 concentration does not completely correspond to the morning and evening peak travel time,but it is delayed.