Air pollution is one of the most concerning environmental issues, in which fine inhalable particles (PM2.5, with diameters that are generally 2.5 micrometers and smaller) concentration plays a key part. Bien Hoa city contains and locates close to several large industrial zones that might create sources of PM2.5 polluting the local air quality. This study monitors and evaluates PM2.5 concentration trends in Bien Hoa airport of Dong Nai province. PM samples are analyzed by Scanning Electron Microscopy (SEM) to recognize the surface pattern and size distributions are analyzed by ImageJ software. Ten samples of PM2.5 were obtained from sampling collected in October 2021. The results show that 24-h PM2.5 mass concentrations were from 15.2 µg/m3 - 50.4 µg/m3 with an average of 28.2 µg/m3; median of 24.1 µg/m3; and standard deviation of 12.2 µg/m3. The values are lower than the Vietnam National Technical Regulation on Ambient Air Quality (QCVN 05:2013/BTNMT) but far higher than the recommended values of the World Health Organization (WHO). SEM and image results indicate the distributions of the particles of 2.0 - 2.5 µm are minor, where the majority are particles with aerodynamic diameter ≤ 1.0 µm. Keywords: Air pollution; Fine particulate matters; PM2.5; Size distribution, Bien Hoa, Dong Nai.

Air pollution is one of the most concerning environmental issues, wherein PM 2.5 concentration plays an important role. This study monitored and evaluated the PM 2.5 concentration trends in Bien Hoa City, Dong Nai Province, Vietnam. Twenty 24-h PM 2.5 samples were continuously collected during the rainy (15 Oct. to 25 Oct. 2021) and dry (19 Mar. to 29 Mar. 2022) seasons. The PM 2.5 samples were analyzed by scanning electron microscopy to determine the surface pattern and size distributions were analyzed using ImageJ software. The water-soluble fractions of 15 trace metal(oid)s concentrations (Al, Cu, Ni, K, Ca, Co, Mn, Cr, As, Zn, Pb, Cd, Na, Fe, and Mg) bound to PM 2.5 were analyzed by inductively coupled plasma-mass spectrometry. The results showed that the 24-h fine fraction PM 2.5 concentrations were 24.1 ± 12.2 μg/m 3 and 63.0 ± 18.7 μg/m 3 in the rainy and dry seasons, respectively. The results indicate that the size distributions of the particles of 2.0–2.5 μm are minor, and the majority are ultrafine particles with aerodynamic diameter ≤ 1.0 μm. Overall, the mass concentration level of the water-soluble fraction of trace metal(oid)s in PM 2.5 in the rainy season was higher than that in the dry season. Among these, Ca, K, and Na were the most abundant earth crustal elements in PM 2.5 in the rainy and dry seasons, accounting for 85% and 41.2% of the total trace element concentrations, respectively. The major sources of PM 2.5 are local and regional sources of thermal power plants, industrial parks, and waterborne transportation (domestic rivers and marine). The activities undertaken to remove Agent Orange (e.g., soil excavation, transportation, and rotary kiln incinerators) at the Bien Hoa airbase area also cause increases in the PM 2.5 level in the atmosphere of Bien Hoa City. Graphical abstract Supplementary Information The online version contains supplementary material available at 10.1007/s11356-022-24801-z.