一个沿海城市大气臭氧的本地生成过程及其对前体物的敏感性

在威海市两个采样点用苏码罐采集了全空气样品,利用三级冷阱预浓缩-GC/MS方法离线测定了空气样品中109种大气挥发性有机物(VOCs).使用基于观测的MCM机理大气化学模式(OBM-MCM)分析了大气臭氧生成对VOCs组分的敏感性及本地生成过程.结果表明:观测期间两个采样点的总挥发性有机物(TVOCs)平均浓度分别为27.84×10~(-9)和17.85×10~(-9),对TVOCs贡献最大的均是烷烃.模拟分析表明,大气臭氧生成与前体物的控制关系存在空间差异性,在一个观测点受VOCs控制,而在另一个观测点受NO_x和VOCs共同控制;模拟结果还表明,臭氧生成对活性烃类最为敏感,但是,含氧有机物、卤代烃和高碳烷烃对臭氧生成的影响和贡献也不可忽视;此外,计算了日平均臭氧净生成速率P(O_3)_(net),分别为6.41×10~(-9) h~(-1)和3.22×10~(-9) h~(-1),臭氧的本地生成过程扮演重要角色.

Sensitivity of ambient atmospheric ozone to precursor species and local formation process in a coastal city

The mixing ratio of 109 volatile organic compounds were analyzed by GC/MS coupled with stainless steel canister sampling and a three-state preconcentration, and the sensitivity of ozone formation to VOCs and local formation process were analyzed using the observation-based MCM mechanism atmospheric chemistry model (OBM-MCM).The results showed that the average concentrations of total volatile organic compounds (TVOCs) at the two observation sites were 27.84×10^-9 and 17.85×10^-9, respectively, and the largest contribution to TVOCs was alkane. The simulation analysis showed that there was spatial difference between the sensitivity to the precursor of ozone, which was controlled by VOCs at one site and jointly controlled by NO_<i>x and VOCs at another site. The simulation results also showed that ozone formation was sensitive to active hydrocarbons, but the influence and contribution of oxygenated organic compounds, halogenated hydrocarbons and high carbon alkanes to ozone could not be ignored. In addition, the daily average net ozone generation rate P(O₃)_net at two sites was 6.41×10^-9 h^-1 and 3.22×10^-9 h^-1, respectively and the local ozone photochemical formation plays a key role in ozone concentration.