北京市城区夏季VOCs变化特征分析与来源解析

Characteristic Analysis and Source Apportionment of VOCs in Urban Areas of Beijing in Summer

精细化的挥发性有机物(VO_③Cs)组分特征和来源分析,可以为科学有效地进行臭氧(O_③)污染防控提供支持.利用2020年夏季7~8月北京城区点位监测的小时分辨率VO_③Cs在线数据,分析高O_③浓度时段和低O_③浓度时段环境受体中VO_③Cs化学特征和臭氧生成潜势(O_③FP),并利用正定矩阵因子分解(PMF)模型进行精细化源解析.结果表明,观测期间监测点φ[总大气挥发性有机物(TVO_③Cs)]平均值为12.65×10^(-9),高O_③时段和低O_③时段φ(TVO_③Cs)平均值分别为13.44×10^(-9)和12.33×10^(-9),O_③FP分别为107.6μg·m^(-3)和99.2μg·m^(-3).观测期间O_③生成受VO_③Cs控制,芳香烃的反应活性最高,对O_③FP贡献排名前三的组分均为异戊二烯、甲苯和间/对-二甲苯.低O_③时段环境受体中VO_③Cs的主要来源包括汽车排放(26.4%)、背景排放(15.7%)、溶剂使用(13.0%)、汽修(12.8%)、二次生成源(9.7%)、生物质燃烧(6.1%)、印刷行业(5.7%)、液化天然气(LNG)燃料车(5.5%)和植被排放(5.0%),其中背景排放、二次生成和印刷行业源在近年来北京VO_③Cs源解析研究中少有讨论.高O_③时段汽修源和二次生成源贡献分别较低O_③时段上升了3.4%和2.6%,汽车排放仍是北京城区最主要的VO_③Cs贡献源.植被排放源从07:00开始上升,在午后达到最高;背景排放源的贡献变化较小;汽车排放和LNG燃料车排放源呈现早晚高峰特征,下午时贡献相对较低.

Refined characterization of volatile organic compound(VOCs)components and source apportionment can provide scientific and effective support for ozone(O_③)pollution prevention and control.Using hourly-resolution VOCs online data monitored at urban sites in Beijing from July to August in 2020,the chemical characteristics of VOCs and ozone formation potential(OFP)in environmental receptors during high and low ozone concentration periods were analyzed,and refined source apportionment was conducted with a positive matrix factorization(PMF)model.The results showed that the averageφ[total volatile organic compounds(TVOCs)]at the monitoring sites during the observation period was 12.65×10^(-9),and theφ(TVOCs)during the high and low ozone concentration periods were 13.44×10^(-9) and 12.33×10^(-9),respectively,with an OFP of 107.6μg·m^(-3)and 99.2μg·m^(-3),respectively.Ozone production was controlled by VOCs,with the highest reactivity of aromatic hydrocarbons and the top three species contributing to OFP being isoprene,toluene,and m/p-xylene.The main sources of VOCs in environmental receptors during low O_③ periods included vehicular emissions(26.4%),background emissions(15.7%),solvent using(13.0%),auto repair(12.8%),secondary generation sources(9.7%),biomass combustion(6.1%),printing industry(5.7%),LNG-fueled vehicles(5.5%),and vegetation emissions(5.0%),of which background emissions,secondary generation,and printing industry sources have been little discussed in recent studies of VOCs source apportionment in Beijing.The contribution of auto repair sources and secondary generation sources increased by 3.4%and 2.6%,respectively,during the high O_③ periods compared to those during the low O_③ periods,and vehicular emissions remained the most significant source of VOCs contribution in the urban area of Beijing.Vegetation emissions rose from 07:00 pm and reach a maximum in the late afternoon.The contribution of background emission sources was less variable;vehicular emissions and LNG-fueled vehicle sources showed a morning and evening peak,with a relatively low contribution in the afternoon.