Concentration of nitrate and ammonium nitrogen in different ecosystems | Koncentrácia dusičnanového a amónneho dusíka v rozdielnych ekosystémoch

This work investigates the effect of forest, agricultural and human settlement ecosystems on the concentrations of N-NO3 –, N-NH4 + in the water course Čaradický potok stream based on the data assembled between 2005–2010. The water flow has its springs in the Pohronský Inovec Mts, and then it crosses the districts Zlaté Moravce and Levice. Analysing the results obtained we can see that the lowest average concentrations of the monitored inorganic nitrogen forms within the whole study period were recorded in a sampling site situated under forest ecosystems of Pohronský Inovec. The average concentration of N-NO3 – in the water Čaradice brook was 2.26 mg dm–3. The highest average concentration for the whole monitoring period was observed in January, the lowest in August. The most remarkable increase in the concentrations of N-NO3 – was found in September 2009, probably related to an intense rainfall before the sampling (20.5 mm on 29th September 2009). Among the sampling sites, the maximum average concentration of N-NO3 – was measured in the sites located in ecosystems under direct influence of human settlements (the villages of Kozárovce and Čaradice). These high values were probably due to a secondary increase in nitrate nitrogen resulting from nitrification of ammonium nitrogen supplied with contaminated sewage effluents (no sewage tanks in these villages). The increase in the average concentration of N-NO3 – in the studied water course was during the entire study period caused both by an permanent grassland agroecosystem (sampling site No. 2) and an arable land agro-ecosystem (sampling site No. 4) located in the water catchment basin. The asset of these agro-ecosystems, however, was lower than the one of the urban ecosystems. By variance analysis, were detected three statistically significant factors (year, season and site) affecting the concentration of nitrate nitrogen. The average concentration of amonium nitrogen during the whole monitoring period represented 0.20 mg dm–3. The lowest concentrations were recorded in winter and the highest in summer. The minimum average concentration was measured in February, the maximum in July. Depending on the sampling site, the highest average concentration values throughout the whole monitoring period were obtained in the sampling sites under human settlements (villages of Kozárovce and Čaradice). The variance analysis for N-NH4 + revealed a statistically highly significant effects of sampling date (month) and site.