Point sources of nutrient pollution in the lowland river catchment in the context of the Baltic Sea eutrophication

Eutrophication is a major problem in the Baltic Sea caused by the inflow of large loads of nutrients. This is largely due to diffuse and point sources of pollution such as wastewater treatment plants (WWTPs), which discharge poorly treated wastewater via rivers to the sea. The paper quantifies the problem of point source pollution in the Pilica River catchment (central Poland), one of the largest, second order subcatchments of the Vistula River. The main objectives of the research were: (i) quantification of nutrients transfer along the Pilica River continuum from the source to the estuary into the Vistula River, and (ii) evaluation of the influence of WWTPs on eutrophication of the Pilica River and the Baltic Sea. The study showed that the average total phosphorus (TP) and total nitrogen (TN) load discharged from the Pilica catchment amounted to 0.057 t TP km−2 and 1.655 t TN km−2, respectively, and was two and three times higher, respectively, compared to the annual average loads in the Polish territory and the Baltic States. Moreover, the paper presents possible solutions of sustainable planning and management in river catchments based on the ecohydrological concept and ecological engineering.