Jihwan Son, Yeosook Kim, Heesun Lee, Minjeong Seo, Yuri Choi, JinA Park, Yongsuk Choi, Ju-Sung Park, Gangwoong Lee
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Abstract
In megacities, road traffic is a major source of particulate matter (PM), requiring a critical understanding of effective air pollution control. Despite existing methods to determine PM emission factors (EFs) of vehicles, accurate estimation of PM emissions under real driving conditions remains challenging. We aimed to assess the EFs of organic aerosol (OA) and equivalent black carbon (eBC) from vehicles through on-road measurements in Seoul, Korea, to understand real-world PM emissions. We used a mobile laboratory equipped with an aerosol mass spectrometer and an aethalometer to measure the composition of PM. On-road measurements were conducted in vehicle tunnels, urban roadways, and residential areas, and the characteristics of measurement points were compared and analyzed. Our results showed that concentrations of OA increased proportionally with the influence of vehicle exhaust, while oxidation states of the OA decreased. Mobile measurements revealed spatial heterogeneities in aerosols, highlighting distinct characteristics of fresh OA on vehicle roads and elevated oxidation state values in residential areas. Active nitrate formation near vehicles led to elevated NO3 concentrations on roads compared to residential areas. Our study shows that mobile PM measurements, including OA and eBC, are valuable for the direct evaluation of emission inventories. However, given that the calculated EFs may not be applicable to other cities due to differences in vehicle composition and traffic conditions, the development of city-specific EFs will be necessary in the future. Furthermore, it is recommended to integrate this methodology with conventional emission inventories to identify vehicle-type-specific emissions.
在特大城市，道路交通是颗粒物（PM）的主要来源，需要对有效的空气污染控制有一个关键的了解。尽管现有方法可以确定车辆的可吸入颗粒物排放系数（EFs），但在实际驾驶条件下准确估算可吸入颗粒物的排放量仍然具有挑战性。我们的目的是通过在韩国首尔进行路面测量，评估车辆产生的有机气溶胶（OA）和等效黑碳（eBC）的排放因子，以了解真实世界的可吸入颗粒物排放情况。我们使用一个配备了气溶胶质谱仪和乙氧基卤化仪的移动实验室来测量可吸入颗粒物的成分。在车辆隧道、城市道路和居民区进行了路面测量，并对测量点的特征进行了比较和分析。结果表明，随着汽车尾气的影响，OA 的浓度成比例增加，而 OA 的氧化态则降低。移动测量揭示了气溶胶的空间异质性，突出显示了车辆道路上新鲜 OA 的独特特征和居民区氧化态值的升高。车辆附近活跃的硝酸盐形成导致道路上的 NO3 浓度高于居民区。我们的研究表明，移动 PM 测量（包括 OA 和 eBC）对于直接评估排放清单很有价值。然而，由于车辆组成和交通状况的不同，计算出的环境系数可能不适用于其他城市，因此未来有必要制定针对具体城市的环境系数。此外，建议将此方法与传统排放清单相结合，以确定特定车辆类型的排放量。
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