POLLUTION SOURCES AND WATER QUALITY STATE OF THE SUPRAŚL RIVER

The main purpose of the study was to evaluate water quality of the Supraśl river and identify its main pollution sources. On the river and its tributaries, 8 control points were selected, located near Krynica, Gródek, Nowosiółki, Zasady (mouth of the tributary Sokołda), Supraśl, Nowodworce, Dobrzyniewo (mouth of the tributary Biała) and Dzikie. The control points were selected in such a way as to take into account the impact of major point sources of analyzed components located along the river and its main tributaries on water quality in the main stream catchment. Water samples were collected once a month during the period from May to November in 2014. In water samples the concentration of dissolved oxygen, Cl^-, SO₄^2-, N-NH₄⁺, P-PO₄^3- and the values of pH, BOD₅ and electrolytic conductivity were indicated. Based on the obtained results, loads of the individual components in river waters were calculated as a product of concentration and Supraśl waters flow rate in a particular month. Supraśl waters, due to values of most analyzed parameters, should be classified as first quality class. The source of Cl^-, SO₄^2-, N-NH₄⁺ in Supraśl waters were treated wastewater and other anthropogenic sources associated with the basin development. Reduced Supraśl water quality is caused by the inflow of organic substances expressed by BZT₅ from natural and anthropogenic origin and concentration of PO₄^3-, which were mainly delivered with treated wastewater