[Studies on the distribution and polycyclic aromatic hydrocarbons of particulate substances in the vicinity of an expressway. Rep. 3. The present condition and properties of diffusion of pollution by polycyclic aromatic hydrocarbons].

In order to clarify synthetically the situation concerning air pollution by suspended particulate matter (SPM) in the vicinity of the Meishin Expressway, polycyclic aromatic hydrocarbons (PAHs), which are typical substances adsorbed on SPM, were determined by the high-performance liquid chromatography method, and the distribution of the PAHs concentrations was examined. The concentration of benzo(a)pyrene (B(a)P) at a point 60 m from the road edge was 2.93 ng/m3 (9.11 micrograms/g dust). The concentration of benzo(ghi)perylene (B(ghi)P) was 6.62 ng/m3 (20.6 micrograms/g dust) at this point, being the highest of all the PAHs that were analyzed in this study. The concentrations of PAHs that were contained in 1 g of dust were the highest in the SPM fraction from 0.7 to 1.6 micron in diameter. The concentrations of PAHs that were contained in particles under 5.4 microns in diameter, and which are absorbed extremely easily into the lung, occupied more than 90% of the concentrations of PAHs that were contained in the total SPM. When there was a high frequency of perpendicular wind, the concentrations of PAHs in SPM fractions under 1.6 micron in diameter showed a marked tendency to have a clear concentration-distance profile, but when there was a high frequency of parallel wind, it was observed that these concentrations at a point 120 m from the road edge were much higher than at the road edge. The correlation coefficient between the concentrations of B(a)P and the traffic volume of large vehicles was elevated with the increase of distance from the road edge and was statistically significant at a point 290 m from the road edge.