Pollution of Small Kaunas Rivers with Biogenic Compounds and Heavy Metals
The pollution of surface water bodies with biogenic compounds and heavy metals is a serious global concern for environment as well as for human health. Therefore, the aim of this study was to investigate the pollution of secondary rivers of Nemunas, flowing in Kaunas city, with respect to concentrations of biogenic nitric and phosphorus compounds as well as heavy metals in water and bottom sediments of the rivers. The samples of water and bottom sediments were taken in the influxes of Sėmena, Girstupis, Marvelė, Vėžpienis and Veršvas. It was investigated the concentrations of inorganic nitric compounds (ammonium, nitrites and nitrates), and phosphates as well as heavy metals (Zn and Cu) in water and bottom sediments. Sėmena was found to be the cleanest river, as it’s ecological state varied from very good (with respect to phosphates) till average (with respect to ammonium). Girstupis was highly polluted with phosphates; however, it has shown relatively good ecological state with respect to nitric compounds. High concentration of phosphates was also found in Veršvas, however, contrary to Girstupis, this river contained exceptionally high concentration of reduced nitric compounds (ammonium). Vėžpienis and Marvelė were the most polluted rivers, most of the nitric and phosphorus compounds exceeded the limit values set in the wastewater management regulations. These rivers were attributed to bad or very bad ecological state with respect to ammonium and good or average ecological state with respect to nitrates and/or phosphates. The concentrations of Zn was relatively low in investigated Kaunas rivers, however, the concentration of Cu was found to be almost 3-times higher than the limit value in Sėmena, Girstupis and Veršvas.