大连市夏季VOCs化学反应活性及来源

为了解大连市环境空气挥发性有机物（VOCs）污染特征及来源，基于2020年6~8月高时间分辨率VOCs在线观测数据，对大连市大气VOCs的浓度水平、组成特征、反应活性及来源情况进行了分析.结果表明φ（VOCs）的平均值为（10.21±5.71）×10^-9，其中烷烃占比为66.35%，烯烃为11.89%，炔烃为7.75%，芳香烃为14.01%.VOCs和NO_x呈现夜间高，白天低的特征，而O₃变化趋势相反.综合考虑物种活性，确定甲苯、乙烯、间/对-二甲苯、1-己烯、正丁烷、异戊烷、正戊烷和异戊二烯是影响大连市大气VOCs的关键物种，优先控制烯烃和芳香烃类化合物的排放是改善大连市夏季O₃污染的关键.PMF源解析结果显示交通源（26.38%）、燃烧源（22.75%）、工业排放源（17.09%）、溶剂使用源（14.59%）、天然源（11.72%）和其他（7.47%）为监测期间VOCs的主要来源，交通源和燃烧源排放是大连市夏季O₃防控的重点污染源.

Chemical Reaction Activity and Source Apportionment of Atmospheric VOCs in Summer in Dalian

To investigate the characteristics and source apportionment of atmospheric volatile organic compounds (VOCs) in Dalian, the concentration level, composition characteristics, reaction activity, and source apportionment of atmospheric VOCs in Dalian were analyzed based on high-resolution online observation VOCs data from June to August 2020. The results showed that the average φ(VOCs) was (10.21±5.71)×10^-9, in which alkanes accounted for 66.35%, alkenes for 11.89%, alkynes for 7.75%, and aromatics for 14.01%. VOCs and NO_x were high at night and low during the day, whereas the change trend of O₃ was opposite. Considering the species activity, it was determined that toluene, ethylene, m/p-xylene, 1-hexene, n-butane, isopentane, n-pentane, and isoprene were the key species affecting atmospheric VOCs in Dalian. Priority control of olefin and aromatic hydrocarbon emissions is the key to improve O₃ pollution in summer in Dalian. By applying the positive matrix factorization (PMF) model, six major VOCs sources were extracted, namely traffic sources (26.38%), combustion sources (22.75%), industrial emission sources (17.09%), solvent usage sources (14.59%), natural sources (11.72%), and others (7.47%). The emissions of traffic sources and combustion sources are the key pollution sources for O₃ prevention and control in Dalian in summer.