Seasonal changes in the concentration of polycyclic aromatic hydrocarbons in azalea leaves and relationship to atmospheric concentration

Seasonal changes in the concentrations of the polycyclic aromatic hydrocarbons (PAH) perylene, benzo[a]pyrene and pyrene in azalea leaves and in the atmosphere (measured separately, in the vapor and particulate phases) were followed at two sites with different traffic conditions in Tokyo. The concentrations of the compounds in the leaves (PAH-lev) and in suspended particulate matter (SPM) (PAH-pat) decreased in summer and increased in winter, whereas the pyrene concentration in the vapor phase decreased from autumn to winter and increased in spring. The concentrations of non-volatile benzo[a]pyrene and perylene in the leaves were approximately proportional to those in SPM. The concentration of volatile pyrene in the leaves was correlated to that in the vapor phase by an equation based on the Langmuir adsorption hypothesis, log[ PAH-vap]/[PAH-lev] = −A/T + B (where A and B are constants and T is temperature), indicating that most of the pyrene in leaves was taken up by adsorption from the vapor phase.