Summary:

The study presents the results of tests on the bottom sediments of the Do-bromierz Reservoir. The reservoir was put into operation in 1986; it is used as flood reservoir and drinkable water reservoir. It is located in the northern part of the catchment of Strzegomka river.
In the bottom sediment samples the following substances were determined: nitrates, nitrites, ammonium nitrogen, organic nitrogen, phosphates, and phos-phorus. The authors also conducted microbiological analyses of the collected se-diments. Cultures of nitrifying and denitrifying bacteria were started. The sediments were analyzed with use of electron microscope. A series of photographs documenting the composition of the sediments were taken.
The test results enable us to claim that the grain size distribution of the se-diments is equivalent to that of silty loam and silty clay loam. The mineralogical composition is dominated by silicates and aluminosilicates - bottom sediments of the Dobromierz reservoir can be classified to the silicate category. The process of denitrification takes place in the sediments. Significantly higher content of phos-phates was found in the bottom sediment than in the benthic waters. The difference in the content in benthic waters and in the sediments causes internal phosphorus loading. During the analyzed period, this process did not cause the acceleration of the eutrophication of the reservoir.