Insight into the levels of fine particulate matter during 2016–2020 in the two largest cities of Vietnam
摘要
Vietnam is currently facing severe air pollution from fine particulate matter (PM2.5). In particular, Ho Chi Minh City (HCM) and Hanoi (HN), the two largest urban centers of Vietnam, frequently rank among the most polluted cities in the world. In this study, hourly PM2.5 data collected from 2016 to 2020 in HCM and HN were comprehensively investigated to assess temporal trends and the effects of long-range atmospheric transport (LRAT) on air quality. The results show that the mean 24-h PM2.5 concentrations exceeded the recommendation guideline of 15 µg/m3 by 82.8 and 93.5% of days in HCM and HN, respectively. Although PM2.5 levels in HCM were significantly lower than those in HN, both cities exhibited a slightly decreasing trend over the five-year period. Seasonal wind patterns were found to play a critical role in pollution dynamics of PM2.5 in both cities. In HCM, southwesterly and westerly winds during the rainy season, and northerly and southeasterly winds during the dry season, were dominant contributors. Meanwhile in HN, northwesterly, northerly, and northeasterly winds influenced PM2.5 levels throughout the year, with particularly strong impacts in winter and spring. The results for LRAT analysis identified northeastern and western regions as major and minor source areas for PM2.5 in Vietnam, respectively, further supported by satellite-based data indicating high pollution levels in these areas. This study emphasizes the demand for long-term monitoring of aerosol particles in Vietnam and implies that air pollution is a transboundary issue requiring international collaborations for effective mitigation strategies.