Zou Y, Yan X L, Flores R M, Zhang L Y, Yang S P, Fan L Y, Deng T, Deng X J, Ye D Q
School of Environment and Energy, South China University of Technology, Guangzhou 510006, China; Institute of Tropical and Marine Meteorology, China Meteorological Administration (CMA), Guangzhou 510640, China.
State Key Laboratory of Severe Weather & Institute of Tibetan Plateau Meteorology, Chinese Academy of Meteorological Sciences, Beijing, China.
Sci Total Environ. 2023 Dec 10;903:166191. doi: 10.1016/j.scitotenv.2023.166191. Epub 2023 Aug 9.
Understanding the sources and impact of volatile organic compounds (VOCs) on ozone formation is challenging when the traditional method does not account for their photochemical loss. In this study, online monitoring of 56 VOCs was carried out in summer and autumn during high ozone pollution episodes. The photochemical age method was used to evaluate the atmospheric chemical loss of VOCs and to analyze the effects on characteristics, sources, and ozone formation of VOC components. The initial concentrations during daytime were 5.12 ppbv and 4.49 ppbv higher than the observed concentrations in the summer and autumn, respectively. The positive matrix factorization (PMF) model identified 5 major emission sources. However, the omission of the chemical loss of VOCs led to underestimating the contributions of sources associated with highly reactive VOC components, such as those produced by biogenic emissions and solvent usage. Conversely it resulted in overestimating the contributions from VOC components with lower chemical activity such as liquefied petroleum gas (LPG) usage, vehicle emissions, and gasoline evaporation. Furthermore, the estimation of ozone formation may be underestimated when the atmospheric photochemical loss is not taken into account. The ozone formation potential (OFP) method and propylene-equivalent concentration method both underestimated ozone formation by 53.24 ppbv and 47.25 ppbc, respectively, in the summer, and by 40.34 ppbv and 26.37 ppbc, respectively, in the autumn. The determination of the ozone formation regime based on VOC chemical loss was more acceptable. In the summer, the ozone formation regime changed from the VOC-limited regime to the VOC-NOx transition regime, while in the autumn, the ozone formation regime changed from the strong VOC-limited regime to the weak VOC-limited regime. To obtain more thorough and precise conclusions, further monitoring and analysis studies will be conducted in the near future on a wider variety of VOC species such as oxygenated VOCs (OVOCs).
当传统方法未考虑挥发性有机化合物（VOCs）的光化学损失时，了解其对臭氧形成的来源和影响具有挑战性。在本研究中，于夏季和秋季臭氧高污染事件期间对56种VOCs进行了在线监测。采用光化学年龄方法评估VOCs的大气化学损失，并分析其对VOCs成分的特征、来源及臭氧形成的影响。白天的初始浓度分别比夏季和秋季观测浓度高5.12 ppbv和4.49 ppbv。正矩阵因子分解（PMF）模型识别出5个主要排放源。然而，忽略VOCs的化学损失导致低估了与高活性VOC成分相关的源的贡献，例如生物源排放和溶剂使用产生的成分。相反，这导致高估了化学活性较低的VOC成分的贡献，如液化石油气（LPG）使用、车辆排放和汽油蒸发。此外，若不考虑大气光化学损失，臭氧形成的估计值可能会被低估。臭氧形成潜势（OFP）方法和丙烯当量浓度方法在夏季分别低估臭氧形成53.24 ppbv和47.25 ppbc，在秋季分别低估40.34 ppbv和26.37 ppbc。基于VOC化学损失确定臭氧形成机制更可接受。夏季，臭氧形成机制从VOC限制机制转变为VOC-NOx过渡机制，而秋季，臭氧形成机制从强VOC限制机制转变为弱VOC限制机制。为得出更全面准确的结论，未来不久将对更多种类的VOCs，如含氧挥发性有机化合物（OVOCs）进行进一步的监测和分析研究。
