Distributions and multiple sources of chlorinated polycyclic aromatic hydrocarbons in the air over Japan.

Chlorinated polycyclic aromatic hydrocarbons (ClPAHs) have been detected in the air at discrete sites in Japan, but there is no information on their distributions throughout Japan. This study was a widespread survey of atmospheric concentrations of ClPAHs throughout Japan. The majority of 24 species of ClPAHs were detected in either the gas or particle phase at all sampling sites. The concentrations were weakly related to human population densities. The relationships between total concentrations of ClPAHs and PAHs suggested that atmospheric ClPAHs at ~70% of the sites were derived from common sources of PAHs. A ternary diagram based on diagnostic ratios of 1-chloropyrene, 7-chlorobenz[a]anthracene, and 6-chlorobenzo[a]pyrene normalized to 3-chlorofluoranthene suggested that waste combustion was the likely source of ClPAHs in summer and that vehicular emissions and coal burning were the likely sources of ClPAHs in winter. A heat map analysis estimated from the concentrations of individual compounds at each site suggested that there were three categories of sources at the sites: i) common sources of ClPAHs and PAHs that had moderate impacts, ii) common sources of ClPAHs and PAHs that had high impacts, and iii) specific sources of ClPAHs.