Particle‐bound composition of polycyclic aromatic hydrocarbons and aerosol carbons in the ambient air

Abstract

Particle‐bound composition and size distributions of organic carbon (OC) , elemental carbon (EC) and polycyclic aromatic hydrocarbons (PAHs) were measured by the PS‐1 sampler, NRI (Noll Rotary Impactor) and MOUDIs (Micro‐orifice Uniform Deposit Impactor) in the ambient air of the traffic intersection and rural site in Ping Tung area of Southern Taiwan from September 1994 to December 1995. Elemental analyzer was used to analyze the carbon composition of aerosol samples. Twenty one individual PAHs were analyzed primarily by a gas chromatography/mass spectrometer (GC/MS) . In the ambient air of Ping Tung area, the aerosol carbons accounted for 18.7%‐25.5% of the total suspended particulate (TSP) mass loading. EC and OC comprised about 12% and 10% of the TSP mass, respectively. The concentration ratios for TC/EC ranged between 1.4 and 2.6 and averaged 2.0 during the sampling periods. More than 80% of particle‐bound composition of 12 potential carcinogenic‐PAHB, namely CYC, BaA, CHR, BbF, BkF, BeP, BaP, PER, IND, DBA, BbC, and BghiP, were existed in the particle size less than 2.5 μm. The size distribution for particle‐bound composition of OC, and EC are all bimodal. The bi‐peaks were all localized at 0.18–0.32 and 1.8–3.2 ranges, respectively. However, the particle size distribution of particle‐bound total‐PAH compositon was found to have trimodal size distribution; the major peaks were localized at 0.05–0.1 μm, 0.18–0.32 μm and 1.8–3.2 μm, respectively, which also mostly belonged to the fine particle mode (Dp < 2.5 μm) . The major peaks for particle‐bound composition of OC, EC and total‐PAHs particle size distribution all located at the fine particle mode indicate not only the gas‐to‐particle condensation in the fine particle mode after those are emitted to the atmosphere but also reveal some important information related to health hazards in the ambient air of traffic intersection. In the ambient air of traffic intersection, the cumulative fraction of carcinogenic‐PAHs and TSP in the particle size less than 1 μm were 71.5% and 15.5%, respectively, while those values in the particle size less than 2.5 μm were 79.5% and 18.6%, respectively. More than 96% of carainogenic‐PAHs were existed in the particle size less than 10 μm. However, more than 68% of TSP were existed in the particle size larger than 10 μm.