PAHs in Chinese atmosphere: Gas/particle partitioning

The gas/particle (G/P) partitioning behavior is an important factor for the environmental fate of polycyclic aromatic hydrocarbons (PAHs) in atmosphere. Based on one year monitoring program at 11 urban sites across China, 7647 pairs of gaseous and particulate concentrations were obtained for 16 priority PAHs, which provided a good opportunity to study the G/P partitioning behavior of PAHs. The concentrations of PAHs in both gas and particle phases were not in the same level among the 11 sites with a difference of more than one orders of magnitude. Along with the increase of molar weight of PAHs, the proportion of concentration in particle phase was increasing. In particle phase, the concentrations of ∑₁₆PAHs in northern Chinese cities were significantly (p < 0.05) higher than those in southern Chinese cities with the average concentrations of 83.4 ± 151 ng/m³ and 33.4 ± 45.5 ng/m³, respectively. However, non-significant difference was found with ∑₁₆PAHs in gas phase. The values of log K_P (the G/P partitioning coefficient/quotient) ranged from −5.65 m³/μg to 2.34 m³/μg, with the mean value of −2.01 ± 1.65 m³/μg for the 16 PAHs. The values of log K_P for individual PAHs at the 11 sites were not in the same level. Furthermore, significant difference (p < 0.05) with log K_P of the 16 PAHs was found between northern Chinese cities and southern Chinese cities except for Acy, Flu and DahA. More than one orders of magnitude difference with K_P were observed for different congeners and different rings PAHs, which are mainly caused by their physical-chemical properties. The results of this study provided large database of K_P, which is necessary and important to the research field of the G/P partitioning of PAHs.