Polycyclic aromatic hydrocarbons and their chlorinated derivatives in atmospheric particles from central Hanoi, Vietnam: Seasonal variation, sources, and regional transport

Abstract

Polycyclic aromatic hydrocarbons (PAHs) and their chlorinated derivatives (ClPAHs) are environmental pollutants that pose significant risks to human health. In this study, total suspended particles were collected during cold and warm periods in central Hanoi, Vietnam, to investigate the occurrence, seasonal variations, emission sources, and potential source regions of particle-bound PAHs and ClPAHs. The mean concentrations of Σ21 PAHs and Σ24 ClPAHs were 80.5 ± 53.9 ng/m3 and 6.92 ± 4.54 pg/m3, respectively, over the entire sampling period. Higher concentrations of both PAHs and ClPAHs were observed in the cold period than in the warm period. Phenanthrene, fluoranthene, and pyrene were the most abundant PAHs. The prevalence of 3–4 ring PAHs was likely attributable to local emissions and long-range atmospheric transport (LRAT), possibly facilitated by particle coating processes during transport. Among ClPAHs, 2-chloroanthracene and 9-chlorophenanthrene predominated, which may reflect atmospheric secondary formation and subsequent LRAT. Diagnostic ratios and non-negative matrix factorization suggested that PAHs were mainly associated with traffic emissions and biomass burning, with smaller contributions from coal combustion, waste incineration, and other industrial activities. Significant positive correlations between Σ21 PAH and Σ24 ClPAH concentrations suggested shared emission sources. Potential source contribution function results identified eastern/northeastern and southwestern regions as potential source areas during the cold and warm periods, respectively. These findings highlight that regional transport of PAHs and ClPAHs may influence air quality in neighboring countries and emphasize the need to consider both local and transboundary sources for effective air pollution mitigation.