Size distribution of airborne particle-bound PAHs and o-PAHs and their implications for dry deposition

Abstract

The present study was conducted to examine the potential mechanisms responsible for the distribution of polycyclic aromatic hydrocarbons (PAHs) and their oxygenated derivatives (o-PAHs) in size fractionated particles and their environmental implications. Size-fractionated atmospheric particles were collected at urban Shanghai, China and analyzed for 5 PAHs and 6 o-PAHs. The concentrations of particle-bound ∑6o-PAHs (sum of 6 o-PAH congeners, 19.1 ± 4.5 ng m⁻³) were significantly higher than those of ∑5PAHs (sum of 5 PAHs, 9.5 ± 1.9 ng m⁻³). The size-fractionated distributions of airborne ∑5PAHs and ∑6o-PAHs displayed bimodal peaks at 0.7–1.1 and 9.0–10.0 μm. Emission sources and volatility were important factors influencing the size distribution of particle-bound 5 PAHs and 6 o-PAHs. The dry deposition fluxes of particle-bound 6 o-PAHs estimated from the measured data (3087 ± 467 ng m⁻² d⁻¹) were approximately 2 times higher than those of PAHs (1531 ± 344 ng m⁻² d⁻¹), with a total deposition flux of 4618 ± 743 ng m⁻² d⁻¹. The relative contributions of particles to dry deposition were also size-dependent, e.g., coarse (aerodynamic diameters (D_p) > 2.1 μm) particles dominated the dry deposition fluxes of PAHs and o-PAHs. These results highlight the significance of providing a comprehensive understanding of particle size distribution of PAHs and o-PAHs and their implication for dry deposition in China.