南宁市冬季挥发性有机物特征及其来源分析

为了解南宁市冬季期间挥发性有机物（VOCs）污染特征及来源，采用在线连续监测系统于2020年12月9日~2021年2月22日在南宁市区对116种VOCs进行了在线连续观测.结果显示，观测期间VOCs体积分数为37.57x10^-9，烷烃、烯烃、芳香烃、OVOCs及卤代烃体积分数占VOCs比例分别为44%、15%、8%、19%和11%.VOCs体积分数白天低，夜晚高；采用OH消耗速率（L_OH）和臭氧生成潜势（OFP）估算了观测期间VOCs大气化学反应活性，结果表明醛酮类、芳香烃和烯烃是主要的活性物质；使用气溶胶生成系数法（FAC）估算了VOCs对二次有机气溶胶（SOA）的贡献，发现芳香烃对SOA生成贡献最大，占比为98%，其中苯、间/对二甲苯和甲苯为优势物种；正交矩阵因子（PMF）解析结果表明，冬季期间南宁市VOCs主要来源于：机动车尾气排放源（30.1%）>固定燃烧及生物质燃烧源（22.2%）>工业工艺排放源（16.8%），而OFP贡献较高的源分别为溶剂使用源（23.9%）、固定燃烧及生物质燃烧源（22%）、机动车尾气排放源（21.8%）.因此，机动车尾气排放源和固定燃烧及生物质燃烧源应为南宁市冬季的优先管控源类，其次为工业工艺排放源、溶剂使用源.

Characteristics and sources of volatile organic compounds (VOCs) in winter over Nanning of China

In order to explore the characteristics and sources of volatile organic compounds (VOCs) pollution in winter, an online continuous monitoring system was used to conduct continuous observation of 116 VOCs in Nanning urban area from December 9, 2020 to February 22, 2021. The results show that the total volume fraction of VOCs was 37.57×10^-9, of which alkanes, olefins, aromatic hydrocarbons, OVOCs and halogenated hydrocarbons accounted for 44%, 15%, 8%, 19% and 11%, respectively, generally being low in the daytime and high at night. In view of the OH radical loss rate (L_OH) and ozone formation potential (OFP), aldehydes and ketones, aromatic hydrocarbons and olefins were thought to be the main active substances. And aromatic hydrocarbons contributed 98% to the generation of secondary organic aerosols (SOA), of which benzene, m/p-xylene and toluene were the dominant species. Then, VOCs mainly derived from the sources in the order as:vehicle exhaust emissions (30.1%) > stationary combustion and biomass combustion (22.2%) > industrial process emissions (16.8%); while the sources with higher OFP contribution were solvent usee (23.9%), stationary- and biomass combustion (22%), and vehicle exhaust emissions (21.8%). Therefore, the priority for controlling VOCs sources in Nanning winter should be firstly placed on the vehicle exhaust emissions and the stationary- and biomass combustion, followed by industrial process emission sources and solvent use sources.