PT06 Organic, Metallic, Organometallic Pollutants
Exhibit Hall
8:00 AM - Tuesday
(PT086) Occurrence, profiles, and photostabilities of chlorinated polycyclic aromatic hydrocarbons associated with particulates in urban air.
Ohura, T1, Kitazawa, A1, Amagai, T1, 1 Institute for Environmental Science, University of Shizuoka, Shizuoka, Japan
ABSTRACT- The atmospheric levels of 12 chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) associated with particulates at an urban site in Japan were investigated. Only 7 of the 12 species studied were detected in air samples collected monthly during 2002. 6-Chlorobenzo[a]pyrene (6-Cl-BaP) was detected at the highest concentration (6.0 pg m-3 (annual mean)), followed by 9,10-dichlorophenanthrene (4.9 pg m-3) and 1-chloropyrene (1-Cl-Py, 3.8 pg m-3). The concentrations of the Cl-PAHs tended to be higher in winter than in summer, with the exception of the 6-Cl-BaP concentration, which was high in both summer and winter. Correlation analysis also indicated that the behavior of 6-Cl-BaP differed significantly from that of the other Cl-PAHs. Comparison of the atmospheric Cl-PAH concentration profile normalized to 1-Cl-Py concentration with that for a traffic air sample revealed significant differences between the profiles. The behavior of the atmospheric Cl-PAHs was also influenced by the origin of the associated particulates, which varied according to season. The positions of chlorination in the detected Cl-PAHs were consistent with those where the frontier electron density was high. This means that the atmospheric Cl-PAHs were formed by secondary reactions with chlorine atoms. The photostabilities of the Cl-PAHs were also investigated in laboratory experiments using a chemical model system. The Cl-PAHs decayed according to pseudo-first-order reaction rate kinetics, with photostabilities increasing in the order 6-Cl-BaP < 1-Cl-Py < 7-Cl-BaA < Cl-Phe < Cl-Fluor, consistent with the trend for the parent PAHs. The photolyses of chlorophenanthrenes and 7-chlorobenz[a]anthracene were confirmed to proceed by initial abstraction of chlorine, followed by oxidative degradation.
Key words: Particulate, Urban air, Cl-PAHs, Photostability