重庆市主城区O3污染时期大气VOCs污染特征及来源解析

2020年8月底至9月初，重庆市主城区发生了持续时间近2周的O₃污染过程.期间，在主城区3个观测站点利用苏玛罐和DNPH采样柱采集的环境空气VOCs样品，研究了O₃污染期间VOCs组分特征、光化学反应活性及来源解析.结果表明，观测期间重庆市主城区TVOCs平均体积分数为45.08×10^-9，各组分体积分数排序依次为OVOCs、烷烃、卤代烃、烯烃、芳香烃和炔烃.体积分数较高的VOCs物种是甲醛、乙烯和丙酮，三者之和占比TVOCs超过30%.OVOCs和烯烃对· OH消耗速率（L_i^·OH）和臭氧生成潜势（OFP）均具有较大的贡献，是生成O₃的关键VOCs组分；其中，OVOCs组分中主要的活性物种为甲醛、乙醛和丙烯醛，烯烃组分中主要的活性物种为异戊二烯、乙烯和正丁烯.VOCs中二甲苯与乙苯的比值较低，并且两者呈现显著的相关性，表明主城区大气中VOCs气团老化程度高，同时还受到其他区域远距离传输的影响.PMF受体模型解析结果显示，主要有5种VOCs来源，依次为二次生成源（27.67%）、机动车尾气源（26.56%）、工业排放源（17.86%）、植物源（14.51%）和化石燃料燃烧源（13.4%）.

Pollution Characteristics and Source Apportionment of Atmospheric VOCs During Ozone Pollution Period in the Main Urban Area of Chongqing

In late August 2020, a period of O₃ pollution occurred in the main urban area of Chongqing and lasted for approximately 2 weeks (till early September). Ambient air samples, collected using Summa Canisters and DNPH sampling columns at three observation sites in the main urban area, were used to study the composition, photochemical reaction activity, and source apportionment of volatile organic compounds (VOCs) during the period of O₃ pollution. The results showed that the mean volume fraction of TVOCs in the main urban area of Chongqing during the observation period was 45.08×10^-9, and the components were ranked by volume fraction in the following order:OVOCs, alkanes, halohydrocarbons, alkenes, aromatics, and alkynes. Formaldehyde, ethylene, and acetone made up the higher volume fraction of VOCs, together accounting for more than 30% of TVOCs. OVOCs and alkenes contributed more to · OH loss rate (L_i^·OH) and ozone formation potential (OFP) and were the key VOCs components for ozone generation. The main active species in the OVOCs component were formaldehyde, acetaldehyde, and acrolein; the main active species in the alkene component were isoprene, ethylene, and n-butene. The ratio of xylene to ethylbenzene in VOCs was low, and they showed a significant correlation, indicating that the VOCs air mass in the main urban area was highly aging and affected by long-distance transmission from other areas. The source apportionment results of the PMF model showed five main sources of VOCs, namely secondary generation (27.67%), vehicle exhaust (26.56%), industrial emission (17.86%), plant (14.51%), and fossil fuel combustion (13.4%).