Diurnal variability of chlorinated polycyclic aromatic hydrocarbons in urban air, Japan

Concentrations of 3- to 5-ring chlorinated polycyclic aromatic hydrocarbons (ClPAHs) and corresponding PAHs were quantified in 3-h integrated air samples, taken serially over 3-day periods in December 2009 (winter) and August 2010 (summer) in the urban area of Shizuoka, Japan. Twenty species of targeted ClPAHs were detected in both gas and particle phases throughout each campaign. Mean concentrations of total ClPAHs in the winter and summer campaigns were 133 ± 53 pg m−3 and 32 ± 27 pg m−3, respectively. Throughout the campaigns, diurnal variations of total ClPAHs concentrations did not have periodic fluctuation such as decreasing in daytime and increasing in nighttime, observed in PAHs. However, the mean concentrations of particulate ClPAHs trended to be slightly higher in nighttime than in daytime, but not for gaseous ClPAHs. Significant correlations were observed between the concentrations of total ClPAHs and total PAHs in particulate phase, but not in gaseous phase. In addition, for particulate phase, there were significant correlations between the concentrations of individual ClPAHs and corresponding parent PAHs, nitrate, and chlorine in summer, but not in winter. Considering these behaviors of ClPAHs in the air, the emission sources could have features of as follows: (i) specific emission sources emitted both ClPAHs and PAHs in particulate phase could be present in the area; (ii) particulate ClPAHs could be more strongly influenced by local sources and photochemical reactions rather than by transboundary air pollution; (iii) the possible sources could be combustion processes included biomass and fossil fuels.