PAHs uptake and translocation in Cinnamomum camphora leaves from Shanghai, China

Foliage uptake and inner-leaf translocation of polycyclic aromatic hydrocarbons (PAHs) by Cinnamomum camphora from different urbanized areas were comparatively investigated in this study. Spatial and seasonal variations of ∑₁₆PAHs in leaves were observed, likely due to the diversity of leaf wax contents sampled in different seasons and locations. A negative correlation between the wax contents and ∑₁₆PAHs concentrations in the cuticular wax was observed. The low values of TF_f-m (translocation factor from foliar dust to mesophyll) indicated a poor translocation ability of PAHs from the foliar dust to the mesophyll. However, the transportation of PAHs from the foliar dust to the cuticular wax was the primary pathway of leaf accumulation, and TF_f-w (translocation factor from foliar dust to cuticular wax) values showed an increasing tendency of low molecular weight (LMW) PAHs and a decreasing tendency of high molecular weight (HMW) PAHs. This result indicated a rapid diffusion of gas-phase PAHs with LMW and a slow desorption of the particle-bound PAHs with HMW in the foliar dust. The concentrations of PAHs pollutants followed an obvious order of Rural area > Suburb area > Urban area in winter, and the higher contaminated locations were associated with some pollution sources nearby. Furthermore, the results of principal component analysis with multiple linear regression analysis analysis indicated that PAHs in leaves derived mainly from vehicle emissions. Overall, the accumulation and transformation of PAHs in leaves suggests the extensive amount of atmospheric pollutant release in high urbanization area.