工业聚集区大气VOCs组成特征及对臭氧生成的影响

运用VOCs在线快速连续自动监测系统,检测了淄博市某工业集聚区大气中59种VOCs组分的浓度。结果表明:观测期间VOCs浓度平均值为(130.74±63.42)×10^-9(以体积分数计,全文同),其中,烷烃占41.17%±17.67%,烯烃占34.22%±23.79%,含硫有机物占12.20%±20.83%,芳香烃占6.70%±10.39%,炔烃占5.75%±6.49 %;烯烃类VOCs活性最高,尤其是乙烯、顺-2-丁烯和丙烯,其参与大气中光化学反应的能力较强。选取VOCs和O₃浓度不同的2个典型时段,用量子化学分子模拟对检出的含硫有机物与羟基自由基(·OH)的前线轨道能量差进行估算,发现甲硫醇、二甲基硫醚和二甲基二硫醚易与·OH发生链引发反应;分析2个时段VOCs组分对O₃生成的影响得出,当烯烃和芳香烃浓度不高时,因含硫有机物浓度增加,O₃浓度仍处于较高水平,含硫有机物是大气中O₃生成的主要贡献物。通过VOCs/NO_x判断敏感性发现,观测期间淄博市O₃生成对VOCs比较敏感,属于VOCs控制区。

Composition characteristics of atmospheric VOCs and the influence on ozone formation in an industrial cluster area

The concentrations of 59 VOCs species in the atmosphere of industrial cluster area in Zibo City was detected using VOCs online rapid continuous automatic monitoring system. The results indicated that the average VOCs concentration was (130.74±63.42)×10-9(volume fraction, the same all the article) during the observation period. The order of volume fraction of each VOCs species was alkanes (41.17%±17.67%),alkenes (34.22%±23.79%),sulphur-containing VOCs (12.20%±20.83%),aromatics (6.70%±10.39%),alkyne (5.75%±6.49%). Alkenes VOCs, especially ethylene, cis-2-butene and propylene, had the highest activity, and had the highest photochemical reactivity. Two typical periods with different VOCs and O3 concentrations were selected to estimate the frontier orbital energy difference between the detected sulphur-containing VOCs and ·OH by quantum chemical molecular simulation. Sulfur-containing VOCs(methyl mercaptan, methyl sulfide, dimethyl disulfide) were more likely to cause chain reactions with ·OH. The effects of VOCs components on ozone formation were analyzed in the two periods, which showed that when the concentrations of alkenes and aromatics were not high, ozone was still at a high level due to the increase of sulphur-containing VOCs concentration, and sulphur-containing VOCs became the main contributors of ozone in the atmosphere. According to the sensitivity of VOCs/NOx, it was found that ozone formation in Zibo City was sensitive to VOCs during the observation period, and Zibo City belonged to VOCs control area.