Characteristics, emissions and source identifications of particle polycyclic aromatic hydrocarbons from traffic emissions using tunnel measurement

Abstract Polycyclic aromatic hydrocarbons (PAHs) in PM 10 and PM 2.5 samples were collected at a road tunnel inlet and outlet in Nanjing, China. Particulate matter and PAHs species mass concentrations, especially higher molecular weight PAHs, both increased noticeably from the tunnel inlet to its outlet. In the tunnel, fluoranthene, pyrene, chrysene, benz[a]anthracene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[ghi]perylene, indeno[1,2,3-cd]pyrene and coronene were abundant PAHs species, all of which were identified as diesel and gasoline vehicle markers. These species had good correlation. Emission factors of higher molecular weight PAHs were significantly higher than those of lower molecular weight PAHs. The PAHs from traffic-related sources were primarily distributed in fine particulate matter compared with coarse particulate matter. Diagnostics ratios and principal component analysis were used to distinguish PAHs sources. The results showed that vehicle exhaust emissions (including those from diesel and gasoline vehicles) contributed 61.66% and 62.22% to the PAHs for PM 10 and PM 2.5 , respectively, while the corresponding values for vehicle non-exhaust emissions (e.g., road dust, brake line, and tyre wear) were 22.09% and 19.34%. PAHs source profiles from vehicles non-exhaust emissions and precise quantitative analysis for PAHs source apportionment from traffic-related sources are both urgently needed.