Apart from widely known anthropogenic pollutants as SO2, NOx, CO2, CO, there are another dangerous substances emitted to the air named polycyclic aromatic hydrocarbons (PAH). In the air they occur in a form of vapours and aerosols deposited on dust particles of 10 μm (PM 10) and 2.5 μm (PM 2.5) in diameter. In cities, the air polluted by gases and atmospheric particulate was analysed using special automatic or semi-automatic equipment or analytic procedures. That is why a powerful development of bioanalytical techniques based on using organisms as bioindicators is observed in recent years. The lichens are the most frequently used organisms in bioindication. The purpose of this research is to evaluate air pollution by PAHs in urban agglomeration with the use of Hypogymnia physodes (L.)Nyl. The research was performed in two hundred thousand occupants in south-east Poland in 2004-2007. The lichens placed on tree branches of 30 cm on 4 crossroads, and the 3 branches were put in each research point. Before starting the exposition, the “O” sample had been collected that had been stored in a closed container before chemical analysis. The exposition period lasted for 3 months. Then PAHs were determined in collected lichens. The analysis was performed with high performance liquid chromatography (HPLC), LiChrosper (TM) column 100 RP - 18, UV detector; λ = 254 nm. The concentration was expressed in mg/kg of dry mass that is after deducting PAH value determined in “O” sample. The analysis of obtained results showed diverse concentration of the pollution in the analysed crossroads depending on the road traffic density and season. PAH concentrations were determined from 0.61 mg·kg-1 d.m. in the 1st quarter of 2004 to 2.56 mg·kg-1 d.m. in the 1st quarter of 2006, and from 0.48 mg·kg-1 d.m. in the 4th quarter of 2004 to 2.22 mg·kg-1 d.m. in the 4th quarter of 2006. Meteorological conditions influence the concentration of PAHs in lichens. The atmospheric precipitation contributed to the decrease of PAHs concentration in the air by scavenging the pollution with atmospheric particulate. The regression line amounted to y = 1.91759 - 0.00674 · x, at the confidence interval equal to p = 0.0308. A relation between the PAH concentration and air relative humidity turned out to be the most essential correlation. This relation indicates that the concentration of PAHs in the lichens increases with an increase of humidity. The line regression amounted to y = -1.04196 + 0.02897 · x, at the confidence interval equal to p = 0.0505.
