| Popis: |
The present article seeks to estimate water pollution with nitrogen and phosphorus and to analyse the territorial specifics in the content of those physicochemical variables along the length of a river. As a case area, the watercourse of the Osam River (Northern Bulgaria) is selected. Data concern the values of the following parameters: ammonium nitrogen (N-NH4), nitrate nitrogen (N-NO3), nitrite nitrogen (N-NO2), total nitrogen (N-tot), orthophosphates (P-PO4), and total phosphorus (P-tot), collected at four sampling points during the period 2015–2020. The assessment is based on the guidelines of Regulation 4/2012 for characterization of the surface waters. The spatial changes in the content of the examined variables are related to land use and for this purpose a map of CORINE Land Cover (2018) is prepared. The resulting information reveals that parameters with the most frequent excesses over the reference norm include N-NO3, N-tot, P-PO4, and P-tot, whose highest observed concentrations remain up to four times above the permissible limits for ”Good status” recommended in Regulation 4/2012. However, the reported values appear to be lower than those established for previous periods, which shows a positive tendency in water quality. There are also spatial features as moving from upstream to downstream – the upper part is contaminated with P-PO4 and P-tot due to the release of raw municipal and industrial effluents, while the lower section is loaded with N-NO3 and N-tot as a result of the excessive fertilization of arable lands. This work enriches past studies with new data for a recent period. |
