SEASONAL VARIABILITY OF SELECTED NUTRIENTS IN THE WATERS OF LAKES NIEPRUSZEWSKIE, PAMIATKOWSKIE AND STRYKOWSKIE
 
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Institute of Land Reclamation, Environmental Management and Geodesy, Poznan University of Life Sciences, Piątkowska 94E, 60-649 Poznań, Poland
CORRESPONDING AUTHOR
Anna Zbierska   

Poznan University of Life Sciences, Institute of Land Reclamation, Environmental Management and Geodesy, Piątkowska 94E, 60-649 Poznań, Poland, Piątkowska 94, 60-649 Poznań, Poland
Publish date: 2016-09-20
 
J. Ecol. Eng. 2016; 17(4):129–137
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ABSTRACT
The paper presents the evaluation of seasonal and long-term changes in selected nutrients of three lakes of the Poznań Lakeland. The lakes were selected due to the high risk of pollution from agricultural and residential areas. Water samples were taken in 6 control points in the spring, summer and autumn, from 2004 to 2014. Trophic status of the lakes was evaluated based on the concentration of nutrients (nitrates, nitrites, ammonium, nitrogen and phosphorus) and indicators of eutrophication. Studies have shown that the concentration of nutrients varied greatly both in individual years and seasons of the analyzed decades, especially in Lakes Niepruszewskie and Pamiątkowskie. The main problem is the high concentration of nitrates. In general, it showed an upward trend until 2013, especially in the spring. This may indicate that actions restricting runoff pollution from agricultural sources have not been fully effective. On the other hand, a marked downward trend in the concentrations of NH4 over the years from 2004 to 2014, especially after 2007, indicates a gradual improvement of wastewater management. Moreover, seasonal variation in NH4 concentrations differed from those of NO3 and NO2. The highest values were reported in the autumn season, the lowest in the summer. Concentrations of nutrients and eutrophication indexes reached high values in all analysed lakes, indicating a eutrophic or hypertrophic state of the lakes. The high value of the N:P ratio indicates that the lakes had a huge surplus of nitrogen, and phosphorus is a productivity limiting factor.