School of Ecology and Environment, Anhui Normal University, Wuhu, 241000, China.
School of Ecology and Environment, Anhui Normal University, Wuhu, 241000, China; Center of Cooperative Innovation for Recovery and Reconstruction of Degraded Ecosystem in Wanjiang City Belt, Wuhu, 241000, China.
Chemosphere. 2023 Jul;328:138609. doi: 10.1016/j.chemosphere.2023.138609. Epub 2023 Apr 4.
Volatile organic compounds (VOCs) emitted from various sources into atmosphere could cause serious O pollution in urban areas. Although characterizations of ambient VOCs have been extensively studied in megacities, they are scarcely investigated in medium/small-sized cities, which could present different pollution characterizations due to the factors like emission sources and populations. Herein, field campaigns were conducted concurrently at six sites in a medium-sized city of Yangtze River Delta region to determine ambient levels, O formations and source contributions of summertime VOCs. During the observation period, the total VOC (TVOCs) mixing ratios ranged from 27.10 ± 3.35 to 39.09 ± 10.84 ppb at six sites. The ozone formation potential (OFP) results showed that alkenes, aromatics and oxygenated VOCs (OVOCs) were dominant contributors, together sharing 81.4% of total calculated OFPs. Ethene ranked the largest OFP contributor at all six sites. A high VOC site, KC, was selected as a case to detailed analyze diurnal variations of VOCs and its relationship with O. Consequently, diurnal patterns varied with VOC groups, and TVOC concentrations were lowest during strong photochemical period (15:00-18:00 p.m.), opposite to the O peak. VOCs/NOx ratios and observation-based model (OBM) analysis revealed that O formation sensitivity was primarily in transition regime in summertime and that the reduction of VOCs rather than NO would be more efficient to suppress O peak at KC during pollution episode. Additionally, source apportionment conducted with positive matrix factorization (PMF) indicated that industrial emission (29.2%-51.7%) and gasoline exhaust (22.4%-41.1%) were major sources for VOCs at all six sites, and that VOCs from industrial emissions and gasoline exhaust were the key precursors for ozone formation. Our results shed light on the importance of alkenes, aromatics and OVOCs in forming O and propose that preferentially reducing VOCs especially those from industrial emission and gasoline exhaust would benefit alleviating O pollution.
挥发性有机化合物（VOCs）从各种源排放到大气中会导致城市地区的严重 O 污染。尽管在特大城市中广泛研究了环境 VOCs 的特征，但在中/小城市中很少进行研究，由于排放源和人口等因素，这些城市可能具有不同的污染特征。在此，在长江三角洲地区的一个中型城市的六个地点同时进行了实地考察，以确定夏季 VOC 的环境水平、O 的形成和来源贡献。在观测期间，六个地点的总挥发性有机化合物（TVOCs）混合比范围为 27.10±3.35 至 39.09±10.84 ppb。臭氧形成潜力（OFP）结果表明，烯烃、芳烃和含氧挥发性有机化合物（OVOCs）是主要贡献者，共同占总计算 OFP 的 81.4%。在所有六个地点，乙烯均为最大 OFP 贡献者。选择高 VOC 站点 KC 作为案例，详细分析 VOC 的日变化及其与 O 的关系。因此，VOC 组的日变化模式不同，TVOC 浓度在强光化学时段（下午 3 点至 6 点）最低，与 O 峰相反。VOC/NOx 比和基于观测的模型（OBM）分析表明，夏季 O 形成的敏感性主要处于过渡状态，在污染期间，减少 KC 中的 VOC 而不是 NO 将更有效地抑制 O 峰。此外，采用正定矩阵因子分解（PMF）进行的源分配表明，工业排放（29.2%-51.7%）和汽油尾气（22.4%-41.1%）是六个站点 VOCs 的主要来源，工业排放和汽油尾气中的 VOCs 是臭氧形成的关键前体。我们的结果表明烯烃、芳烃和 OVOCs 在形成 O 中的重要性，并提出优先减少 VOC 特别是那些来自工业排放和汽油尾气的 VOC 将有助于缓解 O 污染。
