Taršos šaltinių išskyrimas azoto nuostoliams skaičiuoti vidutinio dydžio Lietuvos upėje

Improvement of surface water quality can only be achieved when the amount of pollutants originating from various pollution sources in a watershed is known. The present investigation of nutrient loads from different diffuse and point sources was performed in the Šušvė River catchment. The study included the evaluation of nitrogen load coming from crop fields and animal farms, runoff from forests, discharges from wastewater treatment plant (WWTP), scattered dwellings and from direct atmospheric deposition on surface water bodies, forests clear-cuts and paved surfaces. Measured water runoff as well as nitrogen leaching coefficients for various crop groups and animals were used for the investigation. MONERIS and Source apportionment models were applied for the assessment of nitrogen losses. Despite of some uncertainties of the tested model results they give a realistic picture of the main sources of rivers pollution. Agricultural emission from 746 km2 of agricultural land (64% of the total catchment area) gives 71–68% of the total load depending on a calculation method. Nitrogen load to surface waters originating in crop fields makes up the largest part (51%) of the whole nitrogen load. The second largest source of nitrogen emission are pastures. Pastures and open land make up 52% of agricultural land and make up 27.4% of the total nitrogen emission from agricultural land. N load from scattered dwellings was 82 tonnes per year-1 on the average, i.e. 8% of the total N load. To improve water quality in the Šušvė River, the main attention should be paid on the reduction of nitrogen losses from croplandVytauto Didžiojo universitetasŽemės ūkio akademij