Street dust mercury levels among different land-use categories in Ho Chi Minh city, Vietnam: Source apportionment and risk estimation

Mercury (Hg) in street dust has gained prominent research attention in several regions worldwide owing to its implication as an environmental risk. However, similar studies in Southeast Asia (SEA) remain scarce. In this study, the characteristics, distribution, source apportionment and risk evaluation of Hg in street dust samples collected in 2020 across Ho Chi Minh City (HCMC), were assessed. The average Hg street dust concentration is determined by ICP-MS, at 0.132 ± 0.182 mg kg⁻¹ (n = 96) and being comparable with cities in China and India. Among three land-use categories (industrial–IN, urban–UR and background–BG), IN showed the highest Hg concentration (0.21 ± 0.21 mg kg⁻¹) which was 1.6 and 6-time higher than those of UR and BG, implying the contribution of industrial sectors. Furthermore, a Hg background level of 0.035 ± 0.020 mg kg⁻¹ is proposed for southern Vietnam. Spatial assessment proposed a southwest > northeast Hg concentration gradient within inner HCMC, showing higher Hg fractions over industrial areas and highways than suburban and residential areas. A PMF solution features minor associations of street dust Hg to traffic and combustion activity while highlighting other possible sources or mechanisms (photoreduction, back-partitioning) for street dust Hg in HCMC. A moderate I_geo value for IN sites (0.1 ± 1.6) showed slight Hg enrichment while insignificant non-carcinogenic Hg risk (ΣHI<1) was observed for children and adults. Our study provides important information on street dust Hg level in a southern Vietnam megacity for the establishment of national environmental policies and contributed to the Hg knowledge of SEA region.