The aim of this study was to determine the changes in the course of interception and contact angle curves of the sessile oak occurring in the growing season depending on air pollution. Samples were collected from two areas located in the southern Poland characterized by different degrees of pollution. The first research site was established in a tree stand in the Niepoùomice Forest District, a control area. The second research position was designated in the urbanized part of Cracow, where air pollution with carbon dioxide, sulphur dioxide, trace metals and polycyclic aromatic hydrocarbons (PAHs) is one of the highest in Europe. It was discovered that from July, when the exposure to pollutants is quite long, the surface of leaves starts to erode. Gradual changes in the structure of leaves take place, which consequently alter the values of interception. It is manifested by the fact that values of interception increase with the growth of wettability of plant surface material. Leaf ageing affects water interception but the speed and extent of the changes induced by ageing process are higher in the polluted environment. It was confirmed that interception growth is accompanied by the decrease of a contact angle. The results obtained proved that air pollution in the city, besides seasonal natural variations, cannot be omitted at constructing intercep-tion models.

Keywords: contact angle, polycyclic aromatic hydrocarbons (PAHs), Cracow, urban greening.