北京大气中NO、NO2和O3浓度变化的相关性分析

臭氧（O₃）是城市污染大气中的首要光化学污染物,其变化规律与氮氧化物(NO_x=NO+NO₂)关系密切.采用49C臭氧分析仪和42CTL氮氧化物分析仪对北京城区O₃和NO_x浓度进行了连续观测,时间为2004-08～2005-07.结果显示,O₃和OX（O₃+NO₂）浓度在午后15:00左右出现峰值,NO_x呈双峰态日变化,在07:00和23:00左右出现峰值.不同季节污染物的浓度变化存在差异,O₃和NO_x浓度分别在夏季和冬季达到最大.NO_x浓度存在100×10^-9(体积分数)的“分界点”,NO_x低浓度时以NO₂为主,NO_x高浓度时NO占大部分.OX区域贡献和局地贡献存在明显的季节变化,前者主要受区域背景O₃的影响,在春季最大,后者主要受局地NO_x光化学反应的制约,在夏季最强,同时OX组分呈现显著的昼夜差异.

Analysis of the Relationship between NO, NO2 and O3 Concentrations in Beijing

Ozone (O₃) is a primary gaseous contaminant in urban ambient, and its variation correlates well with nitrogen oxides (NO_x=NO+NO₂). Continuous monitoring in the urban area from August 2004 to July 2005 was carried out in Beijing, using 49C ozone analyzer and 42CTL NO-NO₂-NO_x gas analyzer. The results show that peak O₃ and oxidant (OX=O₃+NO₂) concentrations in Beijing often appear at about 15:00 in the early afternoon, the diurnal variation of NO_x concentrations show a very clear cycle with two peaks, one appears at about 07:00 in the morning and the other is at 23:00 in the evening. However, concentrations variation in four seasons are not same. The highest concentrations of O₃ and NO_x appear in summer and winter, respectively. The NO_x crossover point occurs at about 100×10^-9 volume ratio. At lower level, NO₂ is the major component of NO_x, whereas NO dominates at higher mixing ratio. It is also shown that the level of OX is made up of two contributions, regional contribution and local contribution. The former is affected by regional background O₃ level, with the maximum in spring, whereas the latter is effectively correlates with the level of primary pollution, with the maximum in summer. Diurnal variation also appears in the concentrations of the components of oxidants.