Environment Research Institute, Shandong University, Qingdao, 266237, China; State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing, 100012, China.
Environ Pollut. 2021 Sep 15;285:117162. doi: 10.1016/j.envpol.2021.117162. Epub 2021 Apr 27.
Ground-level ozone (O) has become the principal air pollutant in Beijing during recent summers. In this context, an investigation of ambient concentrations and variation characteristics of O and its precursors in May and June from 2014 to 2017 in a typical urban area of Beijing was carried out, and the formation sensitivity and different causes of heavy O pollution (HOP, daily maximum 8-h O (MDA8h O)>124 ppbv) were analyzed. The results showed that the monthly assessment values of the O concentrations (the 90 percentile MDA8h O within one month) were highest in May or June from 2014 to 2017, and the values presented an overall increasing trend. During this period, the number of O pollution days (MDA8h O > 75 ppbv) also showed an increasing trend. During the HOP episodes, the concentrations of volatile organic compounds (VOCs), nitrogen oxides (NO), and carbon monoxide (CO) were higher than their respective mean values in May and June, and the meteorological conditions were more conducive to atmospheric photochemical reactions. The HOP episodes were mainly caused by local photochemical formation. From 2014 to 2017, O formation during the HOP episodes shifted from VOC and NO mixed-limited to VOC-limited conditions, and O formation was most sensitive to anthropogenic VOCs. Six categories of VOC sources were identified, among which vehicular exhaust contributed the most to anthropogenic VOCs. The VOC concentrations and OFPs of anthropogenic sources have decreased significantly in recent years, indicating that VOC control measures have been effective in Beijing. Nevertheless, NO concentrations did not show an evident decreasing trend in the same period. Therefore, more attention should be devoted to O pollution control in May and June; control measure adjustments are needed according to the changes in O precursors, and coordinated control of VOCs and NO should be strengthened in long-term planning.
近年来，北京夏季首要空气污染物已变为地面臭氧（O）。在此背景下，对 2014 年至 2017 年 5 月和 6 月北京典型城区 O 及其前体物的环境浓度和变化特征进行了调查，并分析了重 O 污染（HOP，日最大 8 小时 O（MDA8h O）>124 ppbv）的形成敏感性和不同成因。结果表明，2014 年至 2017 年 5 月或 6 月的 O 浓度（一个月内 90%的 MDA8h O）月评估值最高，且呈整体上升趋势。在此期间，O 污染天数（MDA8h O>75 ppbv）也呈上升趋势。在 HOP 期间，挥发性有机化合物（VOCs）、氮氧化物（NO）和一氧化碳（CO）的浓度高于 5 月和 6 月的平均值，且气象条件更有利于大气光化学反应。HOP 主要由局地光化学形成所致。2014 年至 2017 年，HOP 期间 O 的形成由 VOC 和 NO 混合限制转变为 VOC 限制，O 的形成对人为 VOC 最敏感。鉴定出 6 类 VOC 源，其中机动车尾气对人为 VOC 的贡献最大。近年来，人为源 VOC 浓度和 OFP 显著降低，表明北京的 VOC 控制措施有效。然而，同期 NO 浓度并未呈现明显的下降趋势。因此，应更加关注 5 月和 6 月的 O 污染控制；需要根据 O 前体物的变化调整控制措施，在长期规划中加强 VOCs 和 NO 的协同控制。
