Conversion of polycyclic aromatic hydrocarbons on diesel particulate matter upon exposure to ppm levels of ozone |
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| Affiliation: | 1. Advanced Radiation Technology Institute, Korea Atomic Energy Research Institute, 29, Geumgu-gil, Jeongup, Jeonbuk 56212, Republic of Korea;2. Department of Food Science and Technology, Kongju National University, 54, Daehak-ro, Yesan, Chungnam 32439, Republic of Korea;3. Korea Ginseng Research Institute, Korea Ginseng Corp., Daejeon 305-805, Republic of Korea;1. Institute of Clean Coal Technology, East China University of Science and Technology, Shanghai 200237, China;2. National Engineering Research Center of CWS Gasification and Coal Chemical Industry (Shanghai), Shanghai 200237, China;1. Institute of Chemical Physics, School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing, 100081, PR China;2. College of Resource and Environment Sciences, Xinjiang University, Urumqi, 830046, PR China;1. College of Pharmacy, CHA University, Pocheon, Korea;2. GINSENG BY PHARM Co., Ltd., Wonju, Korea;3. Department of Pathology, University of Ulsan College of Medicine, Gangneung Asan Hospital, Gangneung, Korea;4. College of Korean Medicine, Gachon University, Seongnam, Korea;5. Natural Products Research Institute, Korea Institute of Science and Technology, Gangneung, Korea |
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| Abstract: | Diesel exhaust particlulate matter samples were collected from a dilution tunnel using a Hi-Vol cascade impactor. The fraction of the aerosol with aerodynamic diameter below 0.5 μm, retained on the glass fiber back-up filter, was exposed to a flow of ozonised particle free air for periods of 0.5–4 h (1.5 ppm of O3, flow rate about 40 m3 h−1).Both exposed and non-exposed reference niters were Soxhlet-extracted with benzene and methanol, and the polycyclic aromatic hydrocarbon fraction (PAH) was isolated by a liquid-liquid partition procedure described in the literature, using cyclohexane and dimethylformamid-water as solvents, modified for quantitative recovery of PAH.The conversion yields of PAH upon exposure to O3 were determined by single ion monitoring mass spectrometry using a fused silica capillary column for their separation.Significant conversion was observed for PAH from molecular weight 226 to 276. Approximate half lives are of the order of 0.5–1 h for most PAH measured. This high reactivity of PAH on a carbonaceous matrix is probably related to the large specific surface of soot particles as well as to their high adsorptive capacity for gaseous compounds. Lower molecular weight PAH up to chrysene also undergo important physical losses by volatilisation and the extent to which chemical transformations occurred could not be determined accurately. Different reactivities are observed for several isomeric pairs of PAH: benzo(a)pyrene is much faster converted than benzo(e)pyrene, benz(a)anthracene reacts faster than chrysene. The benzo-fluoranthenes are most resistant toward O3 attack.The implications of these results with respect to atmospheric degradation of PAH, as well as to the occurrence of artefactual conversion upon Hi-Vol sampling are discussed. |
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