Chiang Ting-Yu, Chen Wei-Nai, Chou Charles C-K, Chang Shih-Yu, Wu Tzu-Shuan
Department of Public Health, Chung Shan Medical University, Taichung 40201, Taiwan.
Research Center for Environmental Changes, Academia Sinica, Taipei 115, Taiwan.
Sci Total Environ. 2023 Dec 15;904:166849. doi: 10.1016/j.scitotenv.2023.166849. Epub 2023 Sep 9.
Variations in the height of the boundary layer have a critical impact on the vertical transport of near-surface aerosols. Variations can affect the interactions between aerosols and clouds/fog by altering the scattering and absorption of solar radiation, significantly changing radiative forcing, convective precipitation, and regional climate. In this study, we simultaneously monitored air pollution and meteorological factors in a flat urban area (YunTech site, 50 m asl) and its peripheral mountainous region (MeiShan site, 980 m asl), analyzed the characteristics of pollutants under different atmospheric conditions, and explored the differences in the chemical reaction mechanisms of aerosols at various altitudes, aiming to clarify the evolution of the boundary layer in urban and suburban areas and its impact on the transport of pollutants. The results show that even without anthropogenic emissions, urban ground-level pollutants could be transported to peripheral mountainous areas through boundary layer height variations and local circulations, such as mountain-valley breezes. The PM concentration was higher at the urban site (average 31.14 ± 14.82μgm) and could be transported aloft by valley winds, leading to the gradual accumulation of daytime PM with an afternoon peak at the mountain site. Moreover, the nitrogen oxidation rate (NOR = [NO]/[NO] + [NO]) exhibited clear site variations, the mountain site (average 0.41 ± 0.20) was higher than the urban site (average 0.19 ± 0.07), likely due to the atmospheric environment with thick clouds/fog and strong oxidation capacity in the mountain area. Our study has verified that aerosol characteristics, origins, formation pathways and transport mechanisms at the two measurement sites are significantly different under different conditions, which provides a theoretical basis for future air pollution prevention and regional climate research.
边界层高度的变化对近地面气溶胶的垂直输送有着至关重要的影响。这些变化能够通过改变太阳辐射的散射和吸收来影响气溶胶与云/雾之间的相互作用，从而显著改变辐射强迫、对流降水和区域气候。在本研究中，我们同时监测了一个平坦城区（云科大站点，海拔50米）及其周边山区（梅山站点，海拔980米）的空气污染和气象因素，分析了不同大气条件下污染物的特征，并探讨了不同海拔高度气溶胶化学反应机制的差异，旨在阐明城区和郊区边界层的演变及其对污染物输送的影响。结果表明，即使没有人为排放，城市地面污染物也能够通过边界层高度变化和诸如山谷风等局地环流输送到周边山区。城区站点的PM浓度较高（平均为31.14±14.82微克/立方米），并且能够被山谷风输送到高空，导致山区白天PM逐渐积累并在下午达到峰值。此外，氮氧化率（NOR = [NO₂]/[NO₂]+[NO]）呈现出明显的站点差异，山区站点（平均为0.41±0.20）高于城区站点（平均为0.19±0.07），这可能是由于山区云雾浓厚且氧化能力强的大气环境所致。我们的研究证实了在不同条件下两个测量站点的气溶胶特征、来源、形成途径和输送机制存在显著差异，这为未来的空气污染防治和区域气候研究提供了理论依据。
