Faculty of Environmental Engineering, Hanoi University of Civil Engineering, Hanoi, Vietnam.
Graduate Institute of Applied Geology, National Central University, Taoyuan, 32000, Taiwan.
Environ Sci Pollut Res Int. 2022 Jun;29(28):41971-41982. doi: 10.1007/s11356-021-16464-z. Epub 2021 Sep 16.
This study investigated the seasonal variations of the ground-based PM concentration measured at an urban site and Terra MODIS satellite-based aerosol optical depth (AOD) in Hanoi, Vietnam, during the year 2016. The findings showed the large differences in terms of the seasonal variation of both PM concentration and columnar AOD. Clearly, the ground-based PM concentrations decreased during the summer period and highly increased during the late fall and winter periods. The Terra MODIS AOD values also decreased in summer, however, significantly increased in spring. Interestingly, the increasing trend of AOD which in contrast to the decreasing trend of PM concentration was found during the spring period, and vice versa for the winter period. The seasonal analysis of meteorological factors including relative humidity (RH), precipitation, and boundary layer height (BLH) as well as regional fire activities expressed that the increased columnar AOD in spring was largely influenced by the hygroscopic growth of aerosol induced by the increased RH, the larger BLH causing the more effective transport and mixing of atmospheric particles to higher altitudes, and especially the intensive fire activities in the Southeast Asian region during the spring period, whereas the significantly increased surface PM concentration in winter was partly attributed to the impact from the highly industrialized and polluted source region in the Pearl River Delta of China. Different from the spring and winter periods, the abundant precipitation amount and the dominance of maritime air masses arrived in Hanoi in summer were the main reasons for the low AOD and surface PM concentration during this period.
本研究调查了 2016 年在越南河内的一个城市站点测量的地面 PM 浓度和 Terra MODIS 卫星气溶胶光学深度 (AOD) 的季节性变化。研究结果表明，PM 浓度和柱 AOD 的季节性变化存在很大差异。显然，地面 PM 浓度在夏季期间降低，而在深秋和冬季期间大幅升高。Terra MODIS AOD 值在夏季也降低，但是在春季显著增加。有趣的是，在春季发现 AOD 的增加趋势与 PM 浓度的降低趋势相反，而在冬季则相反。对包括相对湿度 (RH)、降水和边界层高度 (BLH) 在内的气象因素以及区域火灾活动的季节性分析表明，春季柱 AOD 的增加主要受到 RH 增加引起的气溶胶吸湿性增长的影响，更大的 BLH 导致大气颗粒更有效地输送和混合到更高的高度，特别是在春季东南亚地区的强烈火灾活动，而冬季地表 PM 浓度的显著增加部分归因于中国珠江三角洲高度工业化和污染严重的源区的影响。与春季和冬季不同，夏季丰富的降水量和海洋性气团在河内的主导地位是这一时期 AOD 和地表 PM 浓度较低的主要原因。
