Unveiling the first two-year dataset on the atmospheric deposition of heavy metals in a southern Vietnam megacity: potential driving factors and ecological risk assessment

Abstract

Characterizing atmospheric deposition of heavy metals (HMs) through bulk sampling provides critical insights into environmental pollution patterns in fast-developing urban centers. Despite being a key economic hub in Southeast Asia (SEA), Ho Chi Minh City (HCMC) has received comparatively limited scientific attention regarding atmospheric deposition of HMs. This study reports the first 2 year (2023–2024) observation data of atmospheric deposition of HMs in HCMC. The volume-weighted mean (VWM) concentrations and deposition fluxes exhibit the same decreasing order: Zn (32.9 µg L⁻¹; 59 885 µg m⁻² year⁻¹) > Mn (22.0; 40 151) > Cu (2.16; 3872) > Pb (1.52; 2839) > Ni (0.70; 1271) > Cr (0.42; 765.7) > V (0.19; 349.4) > As (0.09; 173.7). Bulk HM deposition fluxes increase during the rainy season as a result of enhanced rainfall, whereas the concentrations are lower (rainy < dry season), likely due to dilution effects. Seasonal variability in HM deposition is strongly modulated by the East Asian monsoon through its combined effects on air-mass transport pathways and rainfall-driven scavenging. Enrichment factor (EF) assessments, combined with principal component analysis (PCA), identified four major potential contributing factors on rainwater characteristics at HCMC: a mixture of non-combustion traffic sources and industrial sources, combustion sources, crustal sources, and meteorological influences. Ecological risk assessments indicated a low risk for most HMs (E_i < 30), in which Pb exhibits a high risk, accounting for 60% of the total potential ecological risk, implicating industrial emissions as the dominant contributor. This work provides the first quantitative assessment of atmospheric HM deposition in SEA, improving understanding of toxic metal inputs and supporting environmental management in rapidly urbanizing areas.