Comprehensive investigation of polycyclic aromatic hydrocarbons in multiple water types from Hanoi, Vietnam: contamination characteristics, influencing factors, and ecological risks.

Previous studies on the contamination of polycyclic aromatic hydrocarbons (PAHs) in water usually analyzed one specific sample type such as river or lake water. Comprehensive and updated information about the PAH occurrence in various water types is still scarce, especially in emerging and developing countries. In this study, concentrations of 16 priority PAHs were determined in 100 water samples, including canal water (n = 20), lake water (n = 50), river water (n = 15), and tap water (n = 15), collected from Hanoi, Vietnam in 2024. The highest PAH levels (Σ16 PAHs) were detected in canal water (median 246; range 172-329 ng/L), followed by lake water (72.0; 26.1-137 ng/L), river water (32.6; 25.1-59.0 ng/L), and tap water (23.2; 14.1-75.3 ng/L). Low-molecular-weight PAHs (2-3 rings; 84% ± 10% of total 16 PAHs) were more abundant than high-molecular-weight (HMW) compounds (4-6 rings; 16% ± 10%). The most predominant PAHs were naphthalene (56% ± 14%), phenanthrene (17% ± 8%), pyrene (8% ± 7%), and fluoranthene (7% ± 4%). Polycyclic aromatic hydrocarbon profiles in the water samples indicate mixed emission sources of petrogenic inputs and combustion processes. Dilute effect during riverine transport and natural attenuation are closely related to physicochemical properties of PAHs, which probably serve as determinants of the differences in PAH levels and profiles between the sample types. Low-molecular-weight PAHs (notably naphthalene) are more affected by dilution and natural attenuation than HMW compounds because of their higher mobility and lower persistency. Polycyclic aromatic hydrocarbon levels in the surface water samples of this study were markedly lower than the maximum environmental concentrations and predicted no-effect concentrations, implying acceptable risk levels for aquatic ecosystems.