Concentrations of inorganic nitrogen forms in the water in different biotope in the nature reserve alúvium žitavy

Abstract

Over the years 2006-2008, the concentrations of N-NO- 3, N-NH+4, N-NO-2 were evaluated in dependence on sampling time and sampling site in the water of the Nature Reserve (NR) Alúvium (Aluvium) Žitavy, which is situated in the southwestern part of the Slovak Republic. On the basis of the results achieved, we can state that the mean concentration of nitrate nitrogen in the water of the Nature Reserve over the whole monitored period was 3.84 mg dm -3. It represented 92.79% of inorganic nitrogen, the rest being represented by ammonium nitrogen and nitrite nitrogen. The highest mean concentration for the whole monitored period was found in March, and the lowest in June. In dependence on the sampling site, the highest mean N-NO3 concentrations were found in the sampling sites. The sampling site No. 1 was situated on the inflow of the River Žitava into the Alluvium which proves that its important source is the river itself. The sampling site No. 4 was located in the narrowest part of Alluvium, where the river flows very quickly, oxygen is enriched, and therefore nitrification is more intensive. We found out statistically significant influence of the sampling year, month and site on the change in values of concentrations of this qualitative factor by analysis of variance. Ammonium nitrogen was quantitatively the second best represented by inorganic nitrogen. Of the total inorganic nitrogen it represented 5.53%. Its mean concentration over the whole monitored period represented 0.21 mg dm -3. We recorded low concentrations of N-NH+4 over the whole monitored period in the winter months and the high ones in the months of July to September. In dependence on the sampling site we found out maximum mean N-NH+4 concentrations over the whole monitored period in the sampling sites with typical wetland ecosystems (sampling sites 2, 3, 5, 6). By analysis of variance for this indicator, it was found a statistically significant influence of the year, month and the sampling site on the change in its values. Nitrite nitrogen was the last represented from the monitored inorganic nitrogen forms. Of the inorganic nitrogen it represented 1.69%. Lower N-NO-2 concentrations, compared to N-NO - and N-NH3, are probably related to its easy oxidation or reduction in waters. Minimum mean concentrations over the whole monitored period were in March, and April, and the maximum ones were in July. The sampling site had no statistical influence on the changes in N-NO2 - concentrations.