Comprehensive volatile organic compound measurements and their implications for ground-level ozone formation in the two main urban areas of Vietnam
Comprehensive volatile organic compound measurements and their implications for ground-level ozone formation in the two main urban areas of Vietnam
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DOI：
10.1016/j.atmosenv.2021.118872
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发表时间：
2022-01-15
影响因子：
5
通讯作者：
Oram, David
中科院分区：
文献类型：
--
作者：
Hien, To Thi;Huy, Duong Huu;Oram, David
对越南最大和人口最多的两个城市胡志明市和河内的挥发性有机化合物(VOCs)和氧化VOCs(OVOCs)进行了测量。这项研究的目的是为了更好地了解VOC大气的组成及其在地面臭氧形成中的作用。在HCMC和河内的不同季节(旱季和雨季)和河内(春季)，使用多种仪器对各种挥发性有机化合物和其他污染物进行了在线测量。结果表明，河内VOCs总量的平均混合比为80.8&40.7 ppb(平均标准差)，与HCMC雨季(75.2&44.8 ppb)相近。在HCMC的旱季活动期间，与河内活动一致，总VOC减少了约50%(40.7&19.5 ppb)，这主要是由于行星边界层(PBL)高度和盛行风向的增加。两个城市的挥发性有机化合物以烷烃(31-35%)和OVOCs(27-33%)为主，烯烃(13-17%)和芳烃(12-19%)的比例相当。大多数挥发性有机化合物(异戊二烯除外)的日变化在两个城市都有相似之处，在早上(上午7：00-8：00)有两个明显的高峰。和晚上(下午18：00)高峰期，如观察到的车辆燃烧示踪剂(乙炔和一氧化碳)。将成对的挥发性有机化合物(即异/正戊烷和甲苯/苯)的环境比率与摩托车尾气、路边和汽油样本中报告的比率进行比较，结果表明，与摩托车有关的排放可能是造成挥发性有机化合物污染的主要原因。根据丙烯当量浓度(PE Conc.)和最大增量反应性(MIR)法，烯烃和芳烃被确定为反应性和臭氧潜能形成的主要贡献者。此外，基于光化学年龄法估算了VOC物种的初始混合比。消耗的VOCs(初始VOCs减去测量的VOCs)与地面臭氧具有相似的变化趋势，并且在HCMC中有很好的相关性。相比之下，尽管河内的PE conc水平相对较高，但这一结果并未出现。和和平号。
Volatile organic compounds (VOCs) and oxygenated VOCs (OVOCs) were measured in Ho Chi Minh City (HCMC) and Hanoi, the two largest and most populous cities in Vietnam. The purpose of this study is to better understand the VOC atmospheric composition and their role in ground-level ozone formation. Online measurements of a wide range of VOCs and other pollutants were conducted using numerous instruments during different seasons (dry and rainy) in HCMC and Hanoi (spring). Our results show that the mean mixing ratio of total measured VOCs in Hanoi was 80.8 & PLUSMN; 40.7 ppb (mean & PLUSMN; standard deviation), and was similar to that observed during the rainy season (75.2 & PLUSMN; 44.8 ppb) in HCMC. During the dry season campaign in HCMC, which was coincident with the Hanoi campaign, total VOC was around 50% lower (40.7 & PLUSMN; 19.5 ppb), largely a result of increased planetary boundary layer (PBL) height and the direction of the prevailing wind. VOC profiles in both cities were dominated by alkanes (31-35%) and OVOCs (27-33%) and the proportion of alkenes (13-17%) and aromatics (12-19%) were comparable. Similarities in diurnal variation for most VOC species (except for isoprene) are seen in both cities with two clear peaks during the morning (7:00-8:00 a.m.) and evening (18:00 p.m.) rush hours, as observed for vehicular-combustion tracers (acetylene and CO). Comparisons of the ambient ratios of paired VOCs, namely i/n-pentane, and toluene/benzene, with those reported in motorcycle exhaust, roadside and gasoline samples indicate that motorcycle-related emission is likely a major contributor to VOC pollution. According to the propylene-equivalent concentration (PE conc.) and maximum incremental reactivity (MIR) methods, alkenes and aromatics were determined to be the main contributors to reactivity and ozone potential formation. Furthermore, the initial mixing ratio of VOC species was estimated based on the photochemical age method. The consumed VOCs (initial VOCs minus measured VOCs) has a similar variation trend to ground-level ozone, and a good correlation is observed in HCMC. In contrast, this result was not seen in Hanoi despite relatively high levels of PE conc. and MIR.