The paper presents results of the hydroecological investigations of the Vlasina river basin, Serbia (Yugoslavia). The researches were performed in May and September 1996, as a part an annual investigation cycle. Samples were collected from five localities on the Vlasina river, and on two spots on its main tributaries - the Gradska river and Luznica, just before entering into the Vlasina. Qualitative and quantitative data on composition of phyto- and zooplankton, periphytic and benthic communities together with data obtained from physico-chemical water examinations were analysed to assess water quality of examined water courses. The results of performed monitoring were compared with informations on the sources of pollution, as well as with the data on hydrology, geomorphology, demographic variations, and recent development of tourism and industry in the Region in order to assess environmental quality of aquatic ecosystem and to suggest the conservation strategy.

Investigation of air pollution impact on tree condition indicates the greatest correlation between pine defoliation and SO2, SO4 and NH4 concentration in the air, NH4 load with precipitation and its pH in the eastern part of Lithuania. In the southern part significant correlation was found between defoliation and SO4 concentration in the air and SO4, NH4 load with precipitation and its pH. No significant correlation was found in the western region of the country, which includes seaside part. Tree age and tree development classes have an essential effect on the correlation significance

MPI - Metal Pollution Index is being proposed with an aim improving the freshwater pollution control, monitoring and classification based on fish metal body burden. This is a simple mathematical model which enables presentation of Cd, Pb, Cu, Zn and Al fish liver concentration as a single value. After thorough studies of bioaccumulation, biomagnification and tissue distribution patterns, liver of Carassius auratus gibelio has been chosen as sentinel organ. Normal distribution and biological variation assessment is being achieved by using normalizers - reference values (liver concentrations of selected elements in fish from reference sites Vruje and Moharac micro water reservoirs, Serbia (Yugoslavia)). Selected representative sites have been evaluated according to new classification of freshwater ecosystem based on MPI values.

The results indicate that it is possible to reach a good level of reproducibility in a relatively short time. However, quality assurance procedures allow to know the real status of reliability of the field data. More attention must be given to the Level II indices, to select the really useful and informative ones, and to concentrate on these the didactic efforts

The assessment of O3-like foliar symptoms is increasingly considered in monitoring programs aimed at evaluating air pollution effects on forests. The results showed considerable spatial and temporal variation of O3-like foliar symptoms: year, subplot adn the interaction between year and plot were found significant factors. Symptoms resulted lower in 2001; there were differences of foliar symptoms between different subplot and overall the variation between years are considerably different according to the plot being considered. These findings suggest that O3-like foliar symptoms recorded on a small plot selected without a formal statistical approach and with no consideration of the apparently high variability of symptoms expression risk to introduce a serious bias in the evaluation of the potential ozone impact at a given site and its trend