Fluctuations in concentrations of N and P compounds in Marvelė River: a case study of urban pollution

The aim of this study was to evaluate the pollution of the urban stream Marvele, by investigating the seasonal and spatial distribution of the most important nutrients, i.e. ammonium (NH4+-N), nitrates (NO3--N) and phosphates (PO43--P) in water of the river. Marvelė stream is a small 1st type river (catchment area 21,1 km2), left tributary of Nemunas. The valley of the river is situated in both agricultural (upper course), forested (middle course) or densely populated (lower course) areas. Two outfalls discharge surface runoff water from densely populated areas (Aleksotas and other districts) to Marvelė river near the Paupelio street and to a right tributary of Marvelė. As the river flows through residential, green and recreation areas of the city, pollution of Marvelė is a serious problem of Kaunas. Samples of water in the course of the Marvelė river and it’s tributary were collected in February (winter season) and June (summer season). The surface runoff outfall (SRO) in the tributary had stronger effect than the SRO near the Paupelio street. We observed an increased concentrations of NO3--N (28%, p<0.05) in winter and PO43--P (12%, p