A quantitative assessment of source contributions to fine particulate matter (PM_2.5)-bound polycyclic aromatic hydrocarbons (PAHs) and their nitrated and hydroxylated derivatives in Hong Kong

Atmospheric polycyclic aromatic hydrocarbons (PAHs) and their derivatives are of great concern due to their adverse health effects. However, source identification and apportionment of these compounds, particularly their nitrated and hydroxylated derivatives (i.e., NPAHs and OHPAHs), in fine particulate matter (PM_2.5) in Hong Kong are still lacking. In this study, we conducted a 1-year observation at an urban site in Hong Kong. PM_2.5-bound PAHs and their derivatives were measured, with median concentrations of 4590, 44.4 and 31.6 pg m⁻³ for ∑₂₁PAHs, ∑₁₃NPAHs, and ∑₁₂OHPAHs, respectively. Higher levels were observed on regional pollution days than on long regional transport (LRT) or local emission days. Based on positive matrix factorization analysis, four sources were determined: marine vessels, vehicle emissions, biomass burning, and a mixed source of coal combustion and NPAHs secondary formation. Coal combustion and biomass burning were the major sources of PAHs, contributing over 85% of PAHs on regional and LRT days. Biomass burning was the predominant source of OHPAHs throughout the year, while NPAHs mainly originated from secondary formation and fuel combustion. For benzo[a]pyrene (BaP)-based PM_2.5 toxicity, the mixed source of coal combustion and NPAHs secondary formation was the major contributor, followed by biomass burning and vehicle emissions.