Seasonal variability of leaf water capacity and wettability under the influence of pollution in different city zones

Özet

Can dust and tarry substances that are rich in polycyclic aromatic hydrocarbons (PAHs), which are deposited onleaves, cause changes in the water retention of tree crowns? It is hypothesized that the contact angle betweendroplets and a leaf's surface and water capacity changes because of the content of PAHs. This angle is treated as abioindicator of environmental pollution. The goal of this study was to analyse the relationship between rainfallwater capacity and wettability of small-leaved lime and poplar in different zones in a city centre during theperiod from April through November. We implemented a series of simulated rainfall and angle measurementsunder laboratory conditions of tree twigs collected at three locations inside the city centre and one from an areaoutside the city. The background for the water capacity values were results acquired from selected PAHs contentsdetermined in leaves using high-performance liquid chromatography (HPLC), and images of the leaves'surface were acquired via Scanning Electron Microscope (SEM). Based on the obtained results, we concluded thatthere were significant differences in water capacity between the areas for each month. In the city centre, watercapacity from April to July was lower than that in the forested area. From July to the end of the growing season,the water capacity was lower in the city compared to the forest area. The contact angle was strongly correlatedwith water capacity. With a decreasing contact angle, the raindrops increasingly adhered to the leaf surface, andwater capacity increased.It was found that the effects of pollution on water capacity cannot be ignored in developing forecasts or inmodels describing ecosystem and hydrological changes in natural and urbanized environments.