Products of wet and dry deposition of aero-pollutants, reached by over-boundary or internal-boundary transport, are significant source of pollution, almost, whole territory of Serbia (Yugoslavia). Products of wet and dry deposition endangere surface storages in two ways: (1) directly, by deposition on surface storages; (2) indirectly, by deposition on surface of catchment areas, and further transporting through hydrographic system. In the period 1992-1996 investigations were carried out at some localities in Serbia (Yugoslavia). Their results show that recorded quantities significantly over pass MDK (maximal permitted quantity). Investigations included analysis of samples of precipitation (rain and snow), soil and sediment from hydrographic system.

During the period 1977-1996, Oligochaeta have been studied as indicator of water quality in the Bajski canal, Serbia (Yugoslavia). The locality was characterized by the 13 species from nine genera and two families - Naididae and Tubificidae. Species in genera Limnodrilus, Potamothrix and Branchiura were dominant, defining the environment as natural eutrophic.

Low flows are a good measure of the waste water recipient self-purification capability. The regional statistical analysis is an objective way of assessment of the required low flows. This paper presents the principles and key phases of the regional statistical analysis. The advantages of this method are a reduction of the outliers influence and the assessment of low flows on ungauged streams and stream profiles. The method is illustrated with the results obtained by the required low flows regional statistical analysis in Serbia (Yugoslavia) with 59 hydrological gauge stations in the scope, which data has the same length of 39 years, from the year 1956 to 1994.

The aim of this paper is to find out the most efficient method of determination of toxic PCB in the natural way in aquatic system. According to the preliminary research, positive degradative response of PCBs was obtained by the selection of micro fungi species.

Spectrophotometric method for determination of inorganic phosphate liberated in hydrolysis of ATP catalyzed by ATPase was modified in order to obtain faster procedure, which could also be used in none laboratory conditions. The modification has some advantages compared to the most used Pennial method: a) the reagents are stable for several months; b) the 45 min procedure of phosphomolibdate extraction by isobutanole-benzene is ommited, and the method is not dangerous for the analyst; c) color develops after 20 min. The method was tested on the determination of inorganic phosphate in the presence of cadmium nitrate as inhibitor of ATPase activity. The results were compared to the results obtained by Pennial method. The results obtained have shown some good agreements.

Over the last several years, the investigations of the natural zeolites application in the sorption processes have been intensified. Purification of waste waters in order to remove lead, cadmium, copper and other heavy metals, is one significant example of such application. In this paper, the investigations results on characteristics of the natural and chemically activated zeolites from the region of Vranje (Serbia, Yugoslavia), are presented. The experiments with zeolites were performed after determination of their physico-chemical characteristics. Adsorptive characteristics were investigated under laboratory conditions, in a liquid medium, depending on granulation and concentration of the heavy metals. As the obtained results show, these natural materials can be used to remove heavy metals from the waste waters.

The river Timok with its watershed area is one of very imperilled running water on the territory of Serbia (Yugoslavia). By several years investigations of colonies bottoms (phytobenthos, microzoobenthos and macrozoobenthos) and plankton we have found the following: great diversity and specific phytobenthos and bottom fauna (frequency of certain taxa is considerably larger in relation to the other areas, and new taxa have been recorded). Stated specific structure of phytobenthos and bottom fauna have considerably reflected to right estimation of water quality of tested area.

The aim of this paper is to survey and point to the critical parts of this typically valley river in the chosen period of time, which is, because of its low flow, small turbulence and exceptional social and industrial significance, very susceptible to ecological catastrophes. This paper contains the elaborated state of water quality in Yugoslav part of the river Tisza, during two periods of observation, with usual (1988-1991) and specific (1992-1995) river ecosystem exposure to pollutants. The average annual data of concentration for characteristic parameters in the monitoring stations were compared with method of multiobjective iterative compromise optimalization (MICO) of the influence that different categories of polluters have on the river ecosystem. On the basis of analyzed concentrations of selected parameters and results obtained with method of MICO, it is possible to conclude that the improvement in quality of Yugoslav part of the river Tisza has occurred during the period of 1992-1995.

The investigations have been done in Krstonosica shaft at 3 points, in February, May and October 1995, and in January and April 1996. They included algae, Rotatoria, Copepoda, Cladocera, and Hydracarina. The species from divisio Bacillariophyta were presented most among the algal species, with 56 species, then from divisio Chlorophyta, with 26 taxons, Euglenophyta 11, Cyanobacteria 9, Pyrrophyta 3, Xanthophyta 2 and Chrysophyta 1. Among animal groups the highest number belonged to the Rotatoria group, 111 taxons have been determined. The highest number was found during autumn season (86), then in spring (73), and only 14 species in winter. The species that mostly prevailed were phytophyl species. The Cladocera group was present with 18 taxons. The phytophyl species from overgrown plants again prevailed. The Copepoda group was present with 10 species and the phytophyl species were prevailed. According to saprobiological characteristics the greatest number belongs to beta-mezosaprobionts, then oligosaprobionts. A small number of species indicates to the eutrophication process and organic pollution of water.

The work describes optimization on the process of separation of a synthetic dye, methyl orange, from water by sorption on iron(II) hydroxide, using response surface methodology. It was established that the optimum sorption conditions for dye removal on iron(II) hydroxide are: pH 9.1, iron(II) concentration 128 mg/l, dye concentration 10 mg/l, whereby the highest efficiency of dye removal is close to 90%.