Investigation of PM2.5-bound Polycyclic aromatic hydrocarbons (PAHs) and their derivatives (nitrated-PAHs and oxygenated-PAHs) in the roadside environment at the eastern coastal region of China: characterization, source identification, and toxicity evaluation

PM2.5 samples were simultaneously collected in the urban and suburban roadside environments during different traffic flow periods at Qingdao, a coastal city located in China. The composition, diurnal variation, sources, and toxicity of PAHs, NPAHs, and OPAHs in PM2.5 were analyzed to discuss the influence of vehicle emissions on the pollution characteristics of these components. The concentrations of PAHs, NPAHs, and OPAHs in the suburban site were slightly higher than those at the urban site, and the concentrations in winter were about four times higher than those in summer. For PAHs and NPAHs, in urban site, morning rush hours and evening rush hours were the two periods with the highest concentrations compared with other sampling periods, which were consistent with the heavy traffic times. However, in the suburban site, the highest concentration peak appeared in the morning rush hours and the second highest peak appeared at night. Three major sources including coal combustion, gasoline vehicles emissions, and diesel vehicles emissions were identified by PMF. Among these three sources, gasoline vehicle emissions contributed the most in summer and coal combustion contributed the highest fraction in winter. Although the number of diesel vehicles passing through the sampling sites was much less than that of gasoline vehicles, the contribution of diesel vehicles emissions was comparable to that of gasoline vehicles, which indicates that more attention should be paid to the governance of diesel vehicles to reduce the pollution of PAHs and their derivatives in the roadside environments. Traffic sources have a great impact on the toxicity of PAHs and NPAHs.

Automated summary

PM2.5 samples were collected in urban and suburban roadside environments in Qingdao, China, during different traffic flow periods. The analysis of PAHs, NPAHs, and OPAHs in PM2.5 revealed that concentrations were slightly higher in the suburban site and winter compared to the urban site and summer. Peak concentrations for PAHs and NPAHs occurred during morning and evening rush hours in the urban site, while in the suburban site, the highest peak occurred in the morning rush hour and the second highest peak appeared at night. Three major sources, coal combustion, gasoline vehicle emissions, and diesel vehicle emissions, were identified. Diesel vehicle emissions, despite having fewer vehicles, contributed significantly to the pollution of PAHs and their derivatives in the roadside environments. Traffic sources greatly impacted the toxicity of PAHs and NPAHs.