Huong Quang Lea b c✉, Thao Thi Phuong Phama, Le Minh Thuya, Minh Quang Buia c, Trung Quang Nguyend, Nanthapong Chantaraprachoomb, Katsushige Uranishie, Tomohito Matsuob, Akira Kondo
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This study investigated the source apportionment of ambient PM 2.5 and its chemical components in Hanoi, Vietnam, during 2023, using both receptor modeling and regional chemical transport modeling approaches. PM 2.5 samples were collected and analyzed for major water-soluble inorganic ions and trace metals. The observed annual mean PM 2.5 concentrations were 49.2 µg/m 3 (range: 17.0–157 µg/m 3 ), markedly exceeding the WHO annual guideline (5 µg/m 3 ). Secondary inorganic aerosols were the dominant components, with mean concentrations of sulfate (7.8 µg/m 3 ), nitrate (7.9 µg/m 3 ), and ammonium (5.5 µg/m 3 ), whereas chloride was minor (0.2 µg/m 3 ). Among trace metals, Fe (1.7 µg/m 3 ), Mn (0.6 µg/m 3 ), and Zn (0.4 µg/m 3 ) were most abundant. Source apportionment using the Positive Matrix Factorization (PMF) identified six source categories: secondary sulfate (30.7 %), secondary nitrate (23.1 %), traffic emissions (18.1 %), industrial activities (11.1 %), biomass burning (9.7%), and soil dust (7.4%). The Community Multiscale Air Quality (CMAQ) model with the Integrated Source Apportionment Method (ISAM) simulated PM 2.5 concentrations and apportioned contributions from predefined sectors. The largest contributions were attributed to household (H.H, 31.5%), long-range transport (LRT, 23.1%), and industry (IND, 15.5%). Other sources included open biomass burning (OBB, 5.0%), on-road transport (ROA, 3.3%), power generation (POW, 1.8%), natural sources (NAT, 0.4%), other anthropogenic sources (OAN, 5.7%), and non-road traffic (OTR, 0.5%). Although the CMAQ system slightly underestimated PM 2.5 levels (simulated mean 42.7 µg/m 3 vs. observed 48.3 µg/m 3 ), both approaches consistently demonstrated the dominant role of secondary formation and combustion-related emissions in shaping PM 2.5 pollution. PMF directly reflects observation-based chemical signatures at the receptor site, providing explicit secondary factors, whereas CMAQ-ISAM links secondary aerosol to specific sectors and regional transport. Integrating these two methods therefore provides a more comprehensive understanding of PM 2.5 sources in Hanoi and a solid scientific foundation for targeted mitigation strategies.
