imating PAH Dry Deposition by Measuring Gas and Particle Phase Concentrations in Ambient Air

Abstract

Concentrations of the total polycyclic aromatic hydrocarbons (PAHs) in both the gas-phase and particle-phase were measured simultaneously in industrial, urban and suburban areas, and were 1652, 1185, and 834 ng/m super(3), respectively. PAHs with two to four-ring were distributed more than 94% in the gas-phase of all sampling sites. Meanwhile, for PAHs with five to seven-ring, less than 70% were distributed in the gas-phase of the three sites. Approximately two-thirds of the three most hazardous PAHs (BbF + BaP + DBA) were distributed in the gas-phase at the TIP and NCHU, and only one-third of BbF + BaP + DBA were distributed in the gas-phase at the THU. Total dry deposition flux was mainly contributed, with a proportion of between 53.3% and 63.4%, by PAHs with three to four-ring at the three sites. For LMW PAHs, the gas-phase PAHs contribute over 87% to the dry deposition flux at the three sites. Meanwhile, the particle-phase PAHs contribute more than 86% and 99% to the dry deposition flux of the MMW and HMW PAHs, respectively. The mean dry deposition velocities were 0.01, 0.24, 0.47, 0.76, 0.84 and 0.88 cm/s for two to seven-ring PAH homologue. Notably, the dry deposition velocity of the HMW PAHs was significantly higher than that of the LMW PAHs at the three sampling sites. The dry deposition velocities of BbF + BaP + DBA PAHs were 0.8, 0.64 and 1.02 cm/s at the TIP, NCHU and THU, respectively. Accordingly, hazardous PAHs with high dry deposition velocities are threatening to human health by dry deposition.