Particle-phase dry deposition and air-soil gas exchange of polycyclic aromatic hydrocarbons (PAHs) in Izmir, Turkey

Ambient air and dry deposition samples were collected at suburban and urban sites in Izmir, Turkey. Atmospheric total (particle + gas) ∑14PAHs concentrations were 36 ± 39 and 144 ± 163 ng m−3 for suburban and urban sites, respectively. Phenanthrene was the most abundant compound at all sites, and all samples were dominated by low molecular weight PAHs. Average particulate ∑14PAH dry deposition fluxes were 8160 ± 5024 and 4286 ± 2782 ng m−2 day−1 and overall average particulate dry deposition velocities were 1.5 ± 2.4 and 1.0 ± 2.3 cm s−1 for suburban and urban sites, respectively. Soil samples were collected at suburban site. Average soil concentration for ∑14PAH was 55.9 ± 14.4 ng g−1 dry weight. Calculated gas-phase air-soil exchange fluxes indicated that fluorene, phenanthrene, anthracene, and carbazole were deposited to soil in winter while they were volatilized in summer. Other compounds (fluoranthene-benzo[g,h,i]perylene) were deposited to soil in both periods. Annual average fluxes of PAHs representing soil to air (i.e., gas volatilization) and air to soil transfer (i.e., gas absorption, dry deposition, and wet deposition) processes were also compared. All processes were comparable for Σ14PAHs however their input was dominated by gas absorption. Gas absorption dominated for lower molecular weight PAHs, however dry deposition dominated for higher molecular weight PAHs. The results have suggested that for fluorene, soil and air may be approaching a steady state condition. For the remaining compounds, there was a net accumulation into the soil.