Spatial variation and driving mechanism of polycyclic aromatic hydrocarbons (PAHs) emissions from vehicles in China

Rapid motorization has made vehicles become one of the major sources of air pollution and poses substantial risk to human health. Accurate estimation of spatiotemporal variation and driving factors of vehicle emissions will be valuable for pollution control and public health protection. Here, taking polycyclic aromatic hydrocarbons (PAHs) as an example, a dynamic vehicle emission model (DVEM) was developed to assess vehicle emissions. The inventories of vehicle emissions from 2002 to 2017 were estimated under different emission standards and vehicle kilometers traveled for all types of vehicles in China. Vehicle PAHs emissions peaked 1586.85 tonne (t) in 2012 and declined by 36% in the follow-up five years because the vehicle growth has been offset by the upgraded emissions standards. There were remarkable variations among different provinces in China. The vehicle emissions are higher in eastern coastal provinces like Guangdong, Shandong, Jiangsu, and Zhejiang, while lower in the western provinces except Xinjiang. Motorcycles (44.1%) and light duty vehicles (17.8%) were the main contributors to PAHs emissions. The higher urbanization within a region, the larger its vehicle emission density. Urban road density may be linked with the number of on-road vehicles, which is the real driving factor of emissions. Therefore, integrated management should be taken by government to reduce the impacts of vehicle PAHs emissions.