长沙市夏季大气臭氧生成对前体物的敏感性分析

Sensitivity analysis of atmospheric ozone formation to its precursors in summer of Changsha

本文利用长沙市区环境空气质量监测站点在线观测资料,结合罐采样-三级冷阱预浓缩-气相色谱法分析非甲烷烃类化合物和衍生化-高效液相色谱法分析醛酮类化合物,基于观测的光化学模型分析了长沙市区2017年5月和9月部分时段臭氧生成对前体物的敏感性.结果表明,观测期间长沙市区臭氧浓度日变化均呈现典型的单峰特征,峰值浓度出现在15时左右,凌晨高浓度一氧化氮呈现对臭氧明显的滴定效应;5月非甲烷烃浓度和醛酮总浓度较9月高,非甲烷烃主要组成为烷烃和芳香烃类,其次为植物源烃类,而甲醛、乙醛和丙酮为醛酮类化合物主要组分.白天随着光化学过程的发展,非甲烷烃被逐渐消耗,其活性浓度随之降低.模型分析发现:5月份氮氧化物和植物源烃类对长沙市区臭氧生成贡献最大,削减氮氧化物对臭氧控制最为有效;而9月臭氧生成对烯烃和芳香烃最为敏感,削减人为源烯烃和芳香烃对臭氧控制最为有效.

Using on-line observational data from a local ambient air monitoring station in urban Changsha and non-methane hydrocarbons and aldehydes ketones species determined by GC/Dean-switch/FID/FID coupled with a three-stage preconcentration and adsorption tube sampling-high performance liquid chromatography respectively, we applied an observation-based model (OBM) to analyze the sensitivity of typical ozone formation to ozone precursors in May and September 2017. The results showed clear diurnal variation of ozone with typical unimodal distribution and high peak concentration around 15:00, and nocturnal titration effects of enhanced nitric oxide on ozone were obvious in this study. Concentrations of non-methane hydrocarbons, aldehydes and ketones were much higher in May than those in September. In both months the main components of non-methane hydrocarbon were alkanes, aromatics and biogenic volatile organic compounds, and formaldehyde, acetaldehyde and acetone were the most abundant compounds for aldehydes and ketones. As the photochemical processes developed in daytime, non-methane hydrocarbons were consumed gradually and subsequently lowered the activity concentrations. Model analysis found that nitrous oxides and biogenic volatile organic compounds contributed mainly to ozone formation in May, and ozone formation was more sensitive to alkenes and aromatics in September. We therefore propose that abatement of nitrous oxides in May and alkenes and aromatics from anthropogenic sources in September would be an effective way to control ozone in urban Changsha.