Estimation of origins of polycyclic aromatic hydrocarbons in size-fractionated road dust in Tokyo with multivariate analysis.

This study aimed to estimate the origins of polycyclic aromatic hydrocarbons (PAHs) in size-fractionated road dust in Tokyo. First, seven categories of PAHs sources were defined: diesel vehicle exhaust, gasoline vehicle exhaust, tire, pavement, asphalt or bitumen, petroleum products excluding tire and asphalt, and combustion products except for those in vehicle engines. The 189 source data of 12-PAHs profiles were classified into 11 groups based on cluster analysis combined with principal component analysis. Next, 18 road dust samples were collected from eight streets in Tokyo and fractionated into four different particle-size-fractions: 0.1-45, 45-106, 106-250, and 250-2000 microm. In order to estimate the contributions of the classified source groups (S1-S11) to PAHs in the road dust, multiple regression analysis was performed with 12-PAH profile of the road dust as dependent variable and average 12-PAHs profiles of the 11 source groups as 11 explanatory variables. Diesel vehicle exhaust, tire and pavement were the major contributors of PAHs in the fractionated road dust. Although the estimated contributions of the 11 source groups varied among the particle-size-fractions, there was no clear and consistent relationship between particle size and the major PAH contributor.