Gas-Particle Partitioning of PAHs In The Urban Air of Dalian, China: Measurements and Assessments

Abstract

To evaluate the gas-particle partitioning behavior of polycyclic aromatic hydrocarbons (PAHs) in the urban air of Dalian, China, both gas phase and particle phase ambient air were monitored with active high-volume sampler from November 2009 to October 2010. The average total concentration of 16 US EPA priority monitoring PAHs (particle + gas) (∑PAHs) was 112 ng m−3 and the most abundant PAH was Phenanthrene. ∑PAHs and the gas-particle partitioning coefficients (K p) of PAHs displayed seasonal variation in the order of winter > autumn > spring > summer. ∑PAHs was much higher during the heating period than non heating period. ∑PAHs in gas phase were all higher than those in particle phase in the four seasons. The PAHs sources identification was attempted using diagnostic ratios. The relationship between the concentration of PAHs in the air and meteorology parameters were analyzed using SPSS packages. The concentrations of PAHs in the air decreased with the increase of ambient temperature, and increased with the increase of atmospheric pressure. The gas-particle distribution was examined through several different approaches such as the relationship of logK p with the ambient temperature, with the logarithm of the sub-cooled vapor pressure (logP L 0), and the octanol-air partitioning coefficient (logK oa) of PAHs. The slopes obtained from regressing logK p vs. logP L 0 was −0.687∼−0.821 in heating periods, which was in the range between −0.6 and −1, indicating the partitioning of PAHs to particle phase in the urban air of Dalian was absorption as well as for adsorption mechanism. However, the average slope value was −0.502 in the non heating periods, which was shallower than -0.60, indicating that the absorption mechanisms contributed more to the partitioning process. The exposure risk of PAHs was evaluated with four methods, the results of which indicated that the quality of the urban air of Dalian was better.