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Pollution with excess nutrients deteriorate the water quality of the Baltic Sea. The effect of combined land use and climate scenarios on nitrate leaching and nitrogen (N) loads to surface waters from two Baltic Sea catchments (Norsminde in Denmark and Kocinka in Poland) was explored using different models; the NLES and Daisy models for nitrate leaching, and MIKE SHE or MODFLOW/MT3DMS for N transport. Three Shared Socioeconomic Pathways (SSP1, SSP2 and SSP5) defined change in land use and agricultural activities. The climate change scenarios covered 2041–2060 compared with 1991–2010 under RCP8.5, applying four different climate models. Increases in predicted N-load from climate change vary from 20 to 60% depending on climate model. SSPs moderate these N-load changes with small changes for SSP1 to large increases for SSP5, with greater increases for Norsminde than Kocinka due to land use differences. This stresses needs for new measures and governing schemes to meet sustainability targets. [ABSTRACT FROM AUTHOR]

The total nitrogen mass balance was studied over a two-year period in two reservoirs located in south-eastern Poland. The observed nitrogen retention (Nret) in the reservoirs ranged from 0.18 to 2.12 g m-2d-1 (mean 0.83 g m-2d-1) in case of the Rzeszów Reservoir and from -0.02 to 0.41 g m-2d-1 (mean 0.13 g m-2d-1) in case of the Solina Reservoir, while the percentage retention (Nret) ranged from 7 to 42% (mean 22%) and -15 to 73% (mean 35%), respectively. A good relationship between Nret and nitrogen loads was observed for the Solina Reservoir. The data obtained by the author and collected from the researches of 6 other reservoirs located in southern Poland were used to develop an empirical model suitable to predict the nitrogen seasonal dynamics in a reservoir. The model allows for the determination of both the annual mean Nret value and its seasonal variation in a reservoir. [ABSTRACT FROM AUTHOR]