Kim Heejeong, Gil Junsu, Lee Meehye, Jung Jinsang, Whitehill Andrew, Szykman James, Lee Gangwoong, Kim Deug-Soo, Cho Seogju, Ahn Jun-Young, Hong Jinkyu, Park Moon-Soo
Department of Earth and Environmental Sciences, Korea University, Seoul, KR.
Center for Gas Analysis, Korea Research Institute of Standards and Science, Daejeon, KR.
Elementa (Wash D C). 2020;8(46). doi: 10.1525/elementa.444.
To understand the characteristics of air quality in the Seoul Metropolitan Area, intensive measurements were conducted under the Korea-United States Air Quality (KORUS-AQ) campaign. Trace gases such as O, NO, NO, SO, CO, and volatile organic compounds (VOCs), photochemical byproducts such as HO and HCHO, aerosol species, and meteorological variables including planetary boundary layer height were simultaneously measured at Olympic Park in Seoul. During the measurement period, high O episodes that exceeded the 90 ppbv hourly maximum occurred on 14 days under four distinct synoptic meteorological conditions. Furthermore, local circulation such as land-sea breeze and diurnal evolution of the boundary layer were crucial in determining the concentrations of precursor gases, including NO and VOC as well as O. During such episodes, the nighttime NO and VOC and daytime UV levels were higher compared to non-episode days. The overall precursor levels and photochemical activity were represented fairly well by variations in the HCHO, which peaked in the morning during the high O episodes. This study revealed that toluene was the most abundant VOC in Seoul, and its concentration increased greatly with NO due to the large local influence under stagnant conditions. When O was highly elevated concurrently with PM under dominant westerlies, NO and VOCs were relatively lower and CO was noticeably higher than in other episodes. Additionally, the O production efficiency was the highest due to a low NO with the highest NO/NO ratio among the four episodes. When westerlies were dominant in transport-south episode, the nighttime concentration of O remained as high as 40~50 ppbv due to the minimum level of NO titration. Overall, the Seoul Metropolitan Area is at NO-saturated and VOC-limited conditions, which was diagnosed by indicator species and VOC/NO ratios.
为了解首尔大都市区的空气质量特征，在美韩空气质量（KORUS - AQ）行动期间进行了密集测量。在首尔奥林匹克公园同时测量了痕量气体，如O、NO、NO₂、SO₂、CO和挥发性有机化合物（VOCs），光化学副产物如HO₂和HCHO，气溶胶种类，以及包括行星边界层高度在内的气象变量。在测量期间，在四种不同的天气气象条件下，有14天出现了每小时最高值超过90 ppbv的高O₃事件。此外，海陆风等局地环流以及边界层的日变化在确定包括NO和VOC以及O₃在内的前体气体浓度方面至关重要。在这些事件期间，与非事件日相比，夜间的NO和VOC以及白天的紫外线水平更高。高O₃事件期间早晨达到峰值的HCHO的变化很好地反映了总体前体水平和光化学活性。这项研究表明，甲苯是首尔含量最丰富的VOC，在停滞条件下由于较大的局地影响，其浓度随NO大幅增加。在盛行西风且O₃与PM同时大幅升高时，NO和VOCs相对较低，CO明显高于其他事件。此外，由于四种事件中该事件的NO最低且NO₂/NO比率最高，O₃生成效率最高。在输送 - 南风事件中盛行西风时，由于NO滴定水平最低，O₃的夜间浓度高达40~50 ppbv。总体而言，首尔大都市区处于NO饱和和VOC受限的条件，这是通过指示物种和VOC/NO比率诊断出来的。
