Annual Variation of PM_(2.5) Chemical Composition in Ho Chi Minh City, Vietnam Including the COVID-19 Outbreak Period

Ngoc Tran ； Yusuke Fujii ； Vinh Xuan Le ； Nguyen Doan Thien Chi ； Hiroshi Okochi ； To Thi Hien ； Norimichi Takenaka

《Aerosol and Air Quality Research》 23卷5期 (2023/05) Pp. 1-18

https://doi.org/10.4209/aaqr.220312

摘要

PM_(2.5) was continuously collected in Ho Chi Minh City (HCMC), Vietnam, during the period from September 2019 to August 2020, which included the period of socioeconomic suppression caused by restrictions imposed in the face of the coronavirus disease of 2019. The concentrations of PM_(2.5) mass, water-soluble ions (WSIs), organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) were determined to evaluate the seasonal variations in PM_(2.5), the effect of socioeconomic suppression on PM_(2.5), and potential PM_(2.5) sources in HCMC. The PM_(2.5) mass concentration during the sampling period was 28.44 ± 11.55 μg m^(-3) (average ± standard deviation). OC, EC, and total WSIs accounted for 30.7 ± 6.6%, 9.7 ± 2.9%, and 24.9 ± 6.6% of the PM_(2.5) mass, respectively. WSOC contributed 46.4 ± 10.1% to OC mass. NO_3^-, SO_4^(2-), and NH_4^+ were the dominant species in WSIs (72.7 ± 17.7% of the total WSIs' mass). The concentrations of PM_(2.5) mass and total WSIs during the rainy season were lower than those during the dry season, whereas the concentrations of carbonaceous species during the rainy season were higher. The concentrations of PM_(2.5) mass and chemical species during the socioeconomic suppression period significantly decreased by 45%-61% compared to the values before this period. The OC/EC ratio (3.28 ± 0.61) and char-EC/soot-EC (4.88 ± 2.72) suggested that biomass burning, coal combustion, vehicle emissions, cooking activities are major PM_(2.5) sources in HCMC. Furthermore, the results of a concentration-weighted trajectory analysis suggested that the geological sources of PM_(2.5) were in the local areas of HCMC and the northeast provinces of Vietnam (where coal-fired power plants are located).

關鍵字

PM_(2.5) ； Ho Chi Minh City ； COVID-19 ； Vietnam ； CWT