Abstract:

Based on observations of VOCs in the spring and summer of 2023, combined with meteorological data, the composition, pollution, and diurnal variation characteristics of VOCs were analyzed in Taiyuan. The ozone formation potential (OFP) and secondary organic aerosol formation potential (SOAFP) of the VOCs were evaluated using MIR, equivalent propylene concentration, and FAC coefficients. The results showed that the average hourly volume fraction of VOCs in spring and summer was 20.03×10⁻⁹, and alkane and OVOCs were the most abundant components. The total VOCs concentration exhibited a bimodal mode, with peaks occurring at 10:00 and 22:00. The diurnal variation characteristics of alkanes, olefins, acetylene, and aromatic hydrocarbons were consistent with the concentrations of TVOCs; however, OVOCs showed an opposite trend to other VOCs species, indicating that OVOCs were affected by primary emissions and secondary formation. The toluene/benzene (T/B) ratios indicated that the VOCs in the spring and summer in Taiyuan were mainly influenced by vehicle exhaust and biomass combustion. The total SOAFP was up to 25.37×10⁻² μg∙m⁻³, with aromatic hydrocarbons being the dominant species, contributing over 90%. The OFP of the total VOCs reached 49.06×10⁻⁹, and the equivalent propylene concentration was 3.99×10⁻⁹. The order was olefins>OVOCs>aromatics>alkanes>acetylene, indicating that olefins and OVOCs contributed to the formation of O₃. The effective control of paint solvents and industrial production emissions will be conducive to controlling the generation of SOA in Taiyuan. Control of vehicle emissions is an effective measure for reducing O₃ pollution.

Key words: Taiyuan, volatile organic compounds, pollution characteristics, secondary organic aerosol formation potential, ozone formation potential

摘要： 基于太原市2023年春夏季VOCs观测数据，结合同期气象观测资料，分析太原市春夏季VOCs的组成成分、污染特征及其日变化特征，并利用MIR系数、等效丙烯浓度及FAC系数法评估并研究各类VOCs的臭氧生成潜势（OFP）和二次有机气溶胶生成潜势（SOAFP）。结果表明，太原市春夏季大气TVOCs小时平均体积分数为 (20.0±0.87)×10⁻⁹，其中烷烃和含氧有机化合物（OVOCs）是含量最丰富的VOCs组分。太原市TVOCs浓度呈现明显的“双峰型”日变化特征，峰值分别出现在10:00和22:00；从VOCs种类上看，烷烃、烯烃、乙炔和芳香烃与TVOCs浓度的日变化特征较一致，呈现早晚高午后低的变化趋势，OVOCs与其他VOCs物种呈相反的变化趋势。通过φ_(T)/φ_(B)的比值分析发现太原市春夏季大气中VOCs主要受机动车尾气和生物质燃烧源的共同影响。太原市春夏季大气VOCs的SOAFP为25.4×10⁻² μg∙m⁻³，其中芳香烃为绝对优势物种，其贡献率超过90%；TVOCs的OFP为49.1×10⁻⁹，等效丙烯浓度为3.99×10⁻⁹，各VOCs物种的OFP依次表现为烯烃>OVOCs>芳香烃>烷烃>乙炔，表明烯烃和OVOCs对O₃生成具有重要贡献。对涂料溶剂和工业生产排放的有效管控将有利于控制太原市大气中的SOA生成，而控制机动车排放是有效降低O₃污染的有效措施。

关键词: 太原市, 挥发性有机物, 污染特征, 二次有机气溶胶生成潜势, 臭氧生成潜势