北京城区臭氧日变化特征及与前体物的相关性分析

对2012年12月至2013年11月北京城区12个自动空气监测子站的臭氧及其前体物的浓度进行了分析,探讨北京城区臭氧浓度的日变化特征以及与前体物的关系.研究发现,北京市城区臭氧在5~8月份维持相对较高浓度,其他月份则较低.臭氧浓度呈现单峰型分布,基本在15:00、16:00达到峰值;同时臭氧呈现较明显的“周末效应”,即周末臭氧浓度高于工作日浓度. CO、NO、NO2和NOx等前体物多呈现双峰型分布,与O3均呈显著的负相关性,相关性在夏季较低.通过大气氧化剂OX和NOx的拟合方程发现,冬季北京市城区OX在白天受区域O3影响相对较大,在夜间受局地NOx污染影响相对较大.计算了在理想情况下的城区NO2光解速率,春季、夏季、秋季和冬季的平均值分别为0.180,0.209,0.169,0.149min-1.在白天臭氧的高浓度时段城区O3、NO和NO2体现出近似光化学平衡态的特征.

Analysis on diurnal variation characteristics of ozone and correlations with its precursors in urban atmosphere of Beijing

Concentration of ozone and its precursors from 12 automatic air monitoring stations in urban area of Beijing from December 2012 to November 2013 were analyzed to investigate their diurnal changes and correlation. The results showed that ozone concentration maintained relatively high from May to August while it was at a low level in other months. Ozone concentration exhibited a single peak distribution, with the peak appeared around 15:00 and 16:00, and in weekend the concentration was higher than weekdays. Ozone precursors, such as CO, NO, NO2 and NOx, showed bimodal distribution in most cases. Ozone and its precursors showed a negative correlation, and the correlation was weak in summer. According to the fitting equation of OX and NOx concentrations, atmospheric oxidants OX was mainly affected by regional O3 transmission during daytime in winter, and by local NOx pollution during nighttime in winter. The calculated photolysis rate of NO2 in an ideal situation showed that photolysis rate in spring, summer, autumn and winter was 0.180, 0.209, 0.169, 0.149min-1, respectively. The approximate photochemical equilibrium of O3, NO and NO2 was also observed in urban area with high O3 concentration during the day.