Aim of this study was to assess quality of the Danube sediment from the water source "Ratno Ostrvo", which is in the vinicity of the Oil Refinery "Novi Sad" (Serbia, Yugoslavia), after bombardment of the refinery in 1999. In the period March-October 2000, sediment samples were analysed for their oil and oil-derivates contents, i.e. mineral oils contents, by quantitative IR-spectrophotometry, and by qualitative and quantitative GC/MS analyses for their polycyclic aromatic hydrocarbons (PAH) contents. Oil pollution was detected in sediment samples.

Drainage of industrial and communal effluents, directly into the water flow, as many hydrotechnical activities, significantly influence the schedule and balance of the processes that take place into water. In this paper, there are represented the results of systematic control of the water quality of the Danube river and DTD (Danube-Tisza-Danube) channel on the parts Vrbas-Bezdan and Becej-Bogojevo, at the control station network of the Republic Weather Bureau (the Republic of Serbia), for the period of 1991-1996. The results show that the most adverse influence of anthropogenic factor is on the part of the flow of the DTD (Danube-Tisza-Danube) channel from Vrbas to the flow into Tisza river.

Nowadays, different profile of experts are present opinion that surface water quality are exchanged. Type and degree of mineralization content exchange are shown by argumentation. The work have carried out taking into consideration suitability of Danube water for irrigation. The results of chemical investigation from three sample locations (Bezdan, Novi Sad and Banatska Palanka), Serbia (Yugoslavia) during the period 1981-1995, were analyzed. The main statistical parameters and tests of homogeneity are used during the work. Results have pointed put more or less concentration decreasing of analyzed parameters. From statistical point of view, exchange of electrical conductivity and potassium are prominent on all three localities.

The results of long standing and systematic monitoring of quality of river Danube's water, done by the net of stations for controllingquality of water of the Republic Hydrometeorological Service of Serbia (Yugoslavia) are given in this paper. The amount of organic matter (HPK, BPK5), concentration of dissolved oxygen, nutritive matters (NH4(+), NO2(-), NO3(-) and total PO4(3-) and conductivity are specially examined. The results are shown depending on seasonal measuring (average values for spring, summer, autumn and winter) during the period 1995-1998, and the changes are analyzed.

This paper presents the most important results on water quality investigation of the Danube river in the Iron Gate reservoir. The investigations are conducted by the Institute Jaroslav Cerni by means of regular monitoring renewed after a long pause in 2001. The determined phenomena are considered in regard to water quality of the Danube river in the upstream zone.

The results of the examination point out on heterogenity of the phytoplankton community. The presence of 212 taxa has been noted. In the way of quality the green algae are dominant. In all the aspects of the quantitative analysis the domination of Bacillariophyta has been noted, first of all the centric forms. The amount of nutrients on the locality of border with Hungary is considerable, thus during low water and high temperature, the intensive algae development is usual.

The 1st South-Eastern European Interlaboratory Study: WATER ANALYSIS - 2003 was organized by International Scientific Committee on the basis of international European and regional experiences. The total of 38 laboratories took part in WATER-ANALYSIS 2003. Three laboratories were from Greece, two from the Republic of Srpska (Bosnia and Herzegovina), eight from Romania and all others from Serbia and Montenegro. Two samples were prepared from water of the river Danube and the task for participants was to determine trace elements: Al, As, Cd, Cu, Mn, Fe, Pb, and Zn. Results of determination of arsenic (As) and aluminium (Al) are presented in this paper.

Wastewater from the Novi Sad Oil Refinery, Serbia (Serbia and Montenegro) had been previously discharged to the Danube river between the raw water wells. In order to protect water supply source, the collector discharge was displaced downstream, outside the raw water wells area. In 2004, the quality of Danube river water and sediment was monitored at the sites of the old and new collector discharge of the Oil Refinery wastewaters, as well as at two control (reference) sites. The paper presents chemical quality parameters of water and sediment, characterizing oil contamination. Significantly increased contents of oil contaminant were measured in the Danube river sediment at the old discharge site compared to other sampling points, which is a consequence of many-year accumulation, as well as in the Danube river water at the new discharge site, as a consequence of the present wastewater discharge.

Water quality studies of the Danube river in Belgrade region (Serbia and Montenegro) were performed at five locations, in June and September, 2003. Results of the qualitative, quantitative and saprobiological analyses of plankton and macrozoobenthic communities were used for the water quality assessment and the categorization of the watercourse examined. The bioindicator analysis points to the presence of mild organic pollution, water quality varying between the 2nd and 3rd class.