PAH CHARACTERISTICS IN THE AMBIENT AIR OF TRAFFIC-SOURCE

Twenty-seven PAH (polycyclic aromatic hydrocarbon) samples in the ambi ent air of a traffic-source were investigated for their concentration, particle-bound PAH composition, phase distribution, time variation, a nd distance variation. In addition, 18 and 12 PAH samples in the ambie nt air of an urban site and a rural site, respectively, were determine d and compared with those of the traffic-source. The total-PAH concent rations (gas + particle phases) in the ambient air of the traffic-sour ce averaged approximately 5.3 and 8.3 times higher than mean values in the urban and rural atmosphere, respectively. The particle phase dist ribution of total-PAHs averaged 46.1, 18.7, and 20.6% measured at the traffic-source, urban site, and rural site, respectively. The condensa tion process prevailed in the ambient air of the traffic-source. Even though the TSP concentration near the traffic-source averaged only two times higher than the mean value measured on the urban or rural site, the particle-bound composition of 12 potentially carcinogenic PAHs, n amely CYC, BaA, Chr, BbF, BkF, BeP, BaP, PER, IND, DBA. BbC, and BghiP , in the ambient air at the traffic-source averaged approximately 7.8 and 16.5 times higher than those measured at the urban and rural site, respectively. High concentrations of carcinogenic PAHs in the air nea r traffic sources is a strong factor in inducing a high rate of lung c ancer in Taiwan. The results of both time-variation and distance-varia tion investigations show that traffic sources have a very significant impact on urban air quality. The results of PAH analyses of five comme rcial vehicle fuels showed that diesel had the highest total-PAH conce ntration (7341 mg/1). Lower molecular weight PAHs such as Nap, AcPy, a nd Acp were dominant in all vehicle fuels (concentration > 100 mg/1). Comparison of individual-PAH patterns in the vehicle fuels with those in the ambient air of traffic-source showed that a significant fractio n of PAHs was formed during incomplete combustion with thermal synthes is.