[Characteristics and Risk Assessment of Polycyclic Aromatic Hydrocarbons （PAHs） Contamination in Roadside Farmland...

With the increasing development of transportation and the rise of motor vehicle ownership, the problem of polycyclic aromatic hydrocarbons （PAHs） pollution in roadside farmland soils cannot be ignored. This study examined the pollution levels, composition, sources, and health risks of PAHs in farmland soils along with highways in China, based on 16 years of soil data. The results indicated that the median concentration of 16 PAHs in China's roadside farmland soils was 490.15 μg·kg^-1, with a range of 86.40 to 3 568.00 μg·kg^-1. The content of PAH monomers ranged from 5.55 to 47.39 μg·kg^-1 （in median）, with the highest content of phenanthrene. PAHs were mainly composed of medium to high molecular weight compounds （4 to 6 rings）, which accounted for 56.81% of the total PAHs, and the content of PAHs in the majority of the provinces was in the range of "weakly contaminated" or an even higher pollution level. Significant spatial differences exist in the distribution of PAHs, with pollution levels ranging from high to low in northeastern and northwestern regions, central and southeastern coastal regions, and southwestern regions. Environmental climate, industrial development, resource exploitation, and other factors significantly influenced the PAH content in roadside farmland soil. Furthermore, source analysis demonstrated that PAH contamination in roadside farmland soils mainly came from mixed combustion sources of petroleum and natural gas, which was strongly and positively correlated with the local oil and coal reserves. Transport activities related to fossil fuel development have the most significant impact on the PAH content in roadside farmland soil. A comprehensive analysis of the ecological and health risks of PAH contamination was evaluated by three methods, namely the risk quotient, the toxic equivalency factor, and a health risk assessment model, which showed a moderate ecological risk and a low health risk.