Deposition flux of aerosol particles and 15 polycyclic aromatic hydrocarbons in the North China Plain

Abstract

The present study examined deposition fluxes of aerosol particles and 15 polycyclic aromatic hydrocarbons (PAHs) associated with the particles in the North China Plain. The annual mean deposition fluxes of aerosol particles and 15 PAHs were 0.69 ± 0.46 g/(m(2) ×d) and 8.5 ± 6.2 μg/(m(2) ×d), respectively. Phenanthrene, fluoranthene, pyrene, chrysene, benzo[b]fluoranthene, and benzo[k]fluoranthene were the dominant PAHs bound to deposited aerosol particles throughout the year. The total concentration of 15 PAHs in the deposited aerosol particles was the highest in winter but lowest in spring. The highest PAH concentration in the deposited aerosol particles in winter was because the heating processes highly increased the concentration in atmospheric aerosol particles. Low temperature and weak sunshine in winter reduced the degradation rate of deposited aerosol particle-bound PAHs, especially for those with low molecular weight. The lowest PAH concentration in deposited aerosol particles in spring resulted from the frequently occurring dust storms, which diluted PAH concentrations. The mean deposition flux of PAHs with aerosol particles in winter (16 μg/[m(2) ×d]) reached 3 times to 5 times that in other seasons (3.5-5.0 μg/[m(2) ×d]). The spatial variation of the deposition flux of PAHs with high molecular weight (e.g., benzo[a]pyrene) was consistent with their concentrations in the atmospheric aerosol particles, whereas such a phenomenon was not observed for those with low molecular weight (e.g., phenanthrene) because of their distinct hydrophobicity, Henry's law constant, and the spatially heterogeneous meteorological conditions.

Keywords: Aerosol particle; Deposition flux; North China Plain; Polycyclic aromatic hydrocarbons (PAHs).