Concentration of oxygen dissolved in Water Nature Reserve Alúvium Žitavy in the southwestern part of Slovak Republic

Abstract

Over the years 2009–2010, the concentrations of dissolved oxygen depending on sampling time
and sampling site in the water of the Nature Reserve (NR) Alúvium Žitavy, which is situated
in the southwestern part of the Slovak Republic, were evaluated. On the basis of the results we
achieved we can state that its mean concentration in the water of the Nature Reserve over the
whole monitored period was 5.98 mg O 2 dm –3 . Depending on the time of collection, the highest
average oxygen concentration for the whole period of study in March (14.36 mg O 2 dm –3 ) was
found, which is probably related to a high flow and due to turbulent stirring of water as well.
For the whole period of study the lowest average concentrations in the water of the Alúvium
in the summer period were observed with a minimum value being in July (3.36 mg O 2 dm –3 ).
It is supposed that the decrease in oxygen concentration in the summer period with a higher
temperature of water and more intensive decomposition of organic matter by microorganisms was
linked. Depending on the collection places, the highest average concentrations were in collection
sites no. 1 (8.57 mg O 2 dm –3 ), which being located on the inflow of the river Žitavy to the Alúvium
and no. 4 (8.24 mg O 2 dm –3 ), which was located in the narrowest place of the Alúvium with the
fastest water flowing. The lowest average concentrations for the whole period of study in sampling
sites of wetland nature (sampling site no. 2, 3, 5 and 6) were discovered, the lowest average value
being in the sampling site no. 6 (5.31 mg O 2 dm –3 ). The calculated value of the 10th percentile of
this indicator was lower in all sampling sites when compared with that recommended by order of
the Slovak Government No. 269/2010 Coll.