上海城郊夏季大气VOCs在臭氧生成中的作用

Role of Atmospheric VOCs in Ozone Formation in Summer in Shanghai Suburb

为研究上海市夏季臭氧高发季节大气VOCs在臭氧生成中作用,选取2018年5~8月大气臭氧较高的时段,在淀山湖科学观测研究站对103种挥发性有机物、臭氧和氮氧化物等环境污染物进行观测.结果表明,上海臭氧高发季节大气平均φ(VOCs)为32.7×10^(-9),羰基化合物是VOCs的主要组分,所占质量分数达35.0%.羰基化合物中甲醛体积分数最高,其次是丙酮,占12种测量羰基化合物总量的82.8%. 5月环境空气的化学反应活性最强,总的臭氧生成潜势(OFP)为337.2μg·m^(-3),甲醛贡献率最大.烷烃、烯烃和芳香烃的日变化呈现夜高昼低规律,在早晨出现小峰值,与交通排放影响有关;而醛酮类日变化呈现昼高夜低规律,与光化学反应的二次生成过程有关.OBM模拟结果显示,5~6月属于臭氧生成的VOCs控制区,7~8月属于过渡区.

In order to study the role of VOCs in the formation of ozone during the high ozone season in summer in Shanghai, 103 volatile organic compounds, ozone, and nitrogen oxides were measured at state ecology and environment scientific observation and research station for the Yangtze River Delta at Dianeshan Lake from May to August 2018. The average volume fraction of VOCs was 32.7×10^(-9)during the high ozone season in Shanghai. Carbonyl compounds were the main components of VOCs, accounting for 35.0%. Among the carbonyl compounds, the volume fraction of formaldehyde was the highest, followed by acetone, accounting for 82.8% of the total carbonyl compounds. The chemical reaction activity of ambient air was the strongest in May, and the total ozone formation potential(OFP) was 337.2 μg·m^(-3). Formaldehyde had the highest contribution. The examination of the diurnal variations in alkanes, alkenes, and aromatics revealed higher average concentrations at nighttime than at daytime, with a small peak in the morning, which was related to the impact of traffic emissions. Aldehydes and ketones varied diurnally by having higher average concentrations during the daytime than those at nighttime, which was related to the secondary formation process of photochemical reactions. The observation-based model(OBM) showed that O;formation was in a VOC-limited regime from May to June and in a transition regime from July to August.