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Artificial mixing and phosphorus inactivation methods using aluminum compounds are among the most popular lake restoration methods. Długie Lake (Olsztyńskie Lakeland, Poland) was restored using these two methods. Primarily, P precipitation and inactivation methods significantly increased the sorption properties of Długie Lake bottom sediment. Fifteen years after the termination of the restoration procedure, the alum-modified “active” sediment layer still has higher P adsorption abilities, which can limit P internal loading. Relatively low amounts of phosphates in the near-bottom water of Długie Lake, even in anoxia, as well as the fact that the assessed maximum sediment P sorption capacity is still higher than NH4Cl–P (labile P) and BD–P (Fe-bound P) sum (“native exchangeable P”), confirm that hypothesis. Among the tested P adsorption models for the sediment, the double Langmuir model showed the best fit to the experimental data (the highest R2 values). This may indicate that phosphorus adsorption by the tested sediments most likely occurs through phosphate binding at two types of active sorption sites. P adsorption by the studied lake sediment during experiments was significantly connected to aluminum content in sediment. The research into the adsorption properties of sediment can be used as a tool for the evaluation of lake restoration effects.

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tandyRak R., PaRszuto k., GRochowska J., 2016. Water quality of Lake Ełk as a factor connected with tourism, leisure and recreation on an urban area. Quaestiones Geographicae 35(3), Bogucki Wydawnictwo Naukowe, Poznań, pp. 51-59, 4 figs, 3 tables. abstRact: Lake Ełk as an important element of the urban landscape is associated with tourism and active recreation and because of it with the economy of the town. Since 1999 the renovation method with the use of artificial aeration with simultaneous phosphorus inactivation and also as a biological filter -BIO-HYDRO structures were applied on the lake. This process was lasting 10 years and brought only a short-term improvement. At the same time, the shores of the lake were managed to develop of lake tourism: beach, swimming pool, tennis courts, a promenade, and two a water equipment rentals. The illuminated fountain, the road bridge and well -developed catering -accommodation base were made as well.

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