Particle size distribution of polycyclic aromatic hydrocarbons in the city of Venice

Polycyclic aromatic hydrocarbons (PAHs) are important air contaminants, especially in urban areas, characterised by large emissions by road traffic, industries, and domestic heating. In air, PAHs can partition between the gas and the particulate phase because of their relative low vapor pressure. Previous studies focusing on the PAHs size distribution evidenced that PAHs tend to accumulate in fine particles (Hien et al., 2007; Li et al., 2019; Ren et al., 2017). The size of particles where a contaminant is mainly located is a key information for estimating the impact to human health. In fact, the smaller the particles, the deeper they can penetrate the respirator system: nanoparticles (<100 nm) are small enough to pass from the pulmonary epithelium to the circulation, causing more sever damages on human health, with respect to those caused by fine and coarse particles. Several works studied the size distribution of PAHs in aerosol, but most of them focused on a small number of dimensional classes. Since PAHs have been identified as probable or possible carcinogenic compounds, deepening the knowledge about their size distribution becomes essential. In this work the particulate size distribution of PAHs was measured in Autumn 2020 using a cascade impactor MOUDI 110, obtaining twelve different dimensional classes of particles.PAHs were mainly distributed in fine particles (PM1). They showed a bi- or tri peaks in the coarse, in the accumulation, and in the Aitken modes. Passing from low to highmolecular weight PAHs, peaks in the coarse accumulation mode progressively reduce, and the peak in the Aitken mode increases. The same behaviour has been previously observed (Lv et al., 2016; Ren et al., 2017; Wu et al., 2006). Rarely in previous works a peak of PAHs at particle dimensions so close to nanoparticles has been measured. This can be due to the variety of releasing sources, particle aging processes, and conditions occurring in different places or to the different dimensional resolution of the conducted measurements. This means that a thorough investigation of the dimensional distribution of carcinogenic compounds can shed light on their actual danger, which depends not only on their concentration, but also on the size distribution. These preliminary results will be so integrated with further samples in different seasons.We thank Giada D'Errico for her help in the experimental activities (sampling and analysis).ReferencesHien, T.T., Thanh, L.T., Kameda, T., Takenaka, N., Bandow, H. (2007). Atmos. Environ. 41, 1575-1586.Li, H., Li, H., Zhang, L., Cheng, M., Guo, L., He, Q., Wang, X., Wang, Y. (2019). Atmos. Environ. 216, 116924.Lv, Y., Li, X., Ting Xu, T., Tao Cheng, T., Yang, X., Min Chen, J., Iinuma, Y., Herrmann, H. Chem. Phys. 16, 2971-2983.Ren, Y., Zhou, B., Tao, J., Cao, J., Zhang, Z., Wu, C., Wang, J., Li, J., Zhang, L., Han, Y., Liu, L., Cao, C., Wang, G. (2017). Atmos. Res. 183, 322-330.Wu, S.P., Tao, S., Liu, W.X. (2006). Chemosphere 62, 357-367.