The Role of Sources and Atmospheric Conditions in the Seasonal Variability of Particulate Phase PAHs at the Urban Site in Central Poland

The 24-h records of polycyclic aromatic hydrocarbons (PAHs) concentrations in the particulate phase were obtained for the urban site (52.42°N, 16.88°E) in Poznan, one of the largest cities in central Poland, between January and December 2014. The main goal of this study was to identify major emission sources of PAHs congeners and factors controlling their seasonal variability. The most abundant in the particulate matter PAH compound was pyrene (mean concentration of 2.29 ± 4.68 ng m–3, maximum of 22.51 ng m–3), followed by benzo(a)pyrene, dibenz(ah)anthracene, benzo(k)fluoranthene, benzo(b)fluoranthene, phenanthrene, benzo(ghi)perylene, chrysene, benz(a)anthracene and fluoranthene. The results showed a sharp decrease in PAHs concentrations during summer measurements (photodecomposition, high precipitation frequency), and high levels of the quantified PAHs during cold study period (increase anthropogenic emission, low air temperature). During the cold season in 2014, predominant PAHs congeners were: pyrene (26.0%) and 5-ring PAH compounds such as benzo(a)pyrene (19.4%) > dibenz(ah)anthracene (13.7%) ≥ benzo(k)fluoranthene (13.3%) > benzo(b)fluoranthene (9.8%), mostly associated with mixed sources (i.e., combustion, wood burning, industrial emission, traffic emission), whereas during warm study period we observed a large contribution (> 20%) of pyrene, dibenz(ah)anthracene and benzo(a)pyrene in particulate matter. The summertime measurements showed that local emission from the traffic (i.e., diesel and gasoline exhausts) was the second important source of PAHs in aerosol. The coal combustion for residential heating and industrial usage were most pronounced PAHs sources during the entire study period. The multivariate statistical technique (Principal Component Analysis) combined with some diagnostic ratios were applied to provide detailed characteristics of sources and processes related to the polycyclic aromatic hydrocarbons in different seasons. The results from this study are in good agreement with most of the studies focused on seasonal variability of PAHs in the atmosphere.