Seasonal air pollution dynamics, source apportionment, and health risk in industrial zones of southern Vietnam: a five-year integrated assessment

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Abstract
Industrial expansion in southern Vietnam has intensified concerns regarding seasonal air pollution dynamics and associated health risks under tropical monsoon conditions. However, assessments linking interannual variability, source structure, and population-specific health risks in tropical industrial zones remain limited. This study monitored ambient air quality at 37 sites across nine industrial zone clusters in southern Vietnam over five consecutive years (2021–2025), with biannual campaigns during the dry season (March) and rainy season (October). Two-way ANOVA identified significant effects of both year and season on concentrations of PM 10 , SO 2 , NO 2 , CO, NH 3 , and H 2 S (all p < 0.05), with consistently higher dry-season levels, while noise remained invariant. Principal component analysis revealed clear seasonal separation along the primary axis (39.5% variance explained), and hierarchical cluster analysis confirmed season-dominated multivariate structure. Non-negative matrix factorization resolved four stable PM 10 -related source factors, with Factors 3 and 4 showing pollutant signatures consistent with combustion- and sulfur-associated emissions and contributing most strongly during the dry season. The observed seasonal patterns are associated with differences in meteorological conditions and emission activities between the dry and rainy seasons. Probabilistic assessment identified H 2 S, PM 10 , and NO 2 as dominant risk drivers, among which H 2 S posed the greatest exposure concern across population groups, with a mean hazard quotient (HQ) reaching 10.26 in the dry season for the high-exposure group and P (HQ ⩾ 1) ≈ 1.000. GIS-based composite pollution mapping further revealed persistent high-risk hotspots in the East–Southeast industrial corridor, where high-risk area coverage increased from 27% in 2021 to approximately 36% during 2022–2025, a pattern spatially associated with industrial clustering, transport connectivity, and seasonal meteorological conditions. Overall, the findings suggest that the observed seasonal differences in source-related pollutant patterns, pollutant accumulation, and population health risk are consistent with the combined influence of meteorological conditions and seasonal emission activities in tropical industrial environments, providing evidence to support season-specific emission control and targeted public health protection strategies.

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