Nemunas river pollution with biogenic compounds in Kaunas city

Abstract

Water pollution induces adverse effects on ecosystems, disturbing them in various ways. Pollution of water bodies with biogenic (mainly nitrogen and phosphorus) compounds do not cause direct noxious impact on living organisms. However, an excess of it leads to eutrophication: intensive development of phytoplankton, disruption of the gas regime, sedimentation of bottom sediments and, eventually, to the shift in ecosystem composition and drastic reduction in water quality. Therefore the aim of this study was investigate the concentrations of ammonium (NH4+-N), nitrites (NO2--N) and phosphates (PO43-- P) in Nemunas river in different areas of Kaunas city. Water samples were taken in November 2017 in the following regions: Petrašiūnai (0,2 km below Kaunas hydropower plant (HP)), Panemunė (3 km below HP), Jiesia (8 km below HP), Freda (11 km below HP), City center (13 km below HP), Marvelė (17 km below HP) and Zapyškis (30 km below HP). The level of all investigated biogenic compounds tended to decrease going downstream the river from Panemunė and/or Freda district till the suburban area in Zapyškis village. Nevertheless, in the majority of sampling points the concentrations of N and P compounds exceeded the limit values. The highest concentration of NH4+-N (above the limit value of 1mg/l) was found in Panemunė and Freda districts. Similarly, the NO2--N was higher than the limit value (0,03 mg/l) in the districts of Petrašiūnai, Freda and City center. Whereas the highest concentrations of PO43-- P was observed in the lower parts of the river (Jiesia, City center and Marvelė). Relatively lower concentration of phosphates in Petrašiūnai and Panemunė dictricts could be explained by accumulation of P in Kaunas reservoir, above Kaunas HP. Summarizing the results of this study it should emphasized, that Nemunas river is severely polluted with N and P compounds due to diffuse pollution from Kaunas city, [...]