Characteristics of Spatial Distribution of Phosphorus and Nitrogen in the Bottom Sediments of the Water Reservoir Poraj

The aim of this study was to determine the content of phosphorus and nitrogen in the bottom sediments of the Poraj Reservoir located on the Warta River, along with defining their spatial distribution and the relationship between these elements and organic matter, aluminum and iron. Samples of bottom sediments were collected on the basis of regular measurement grid of 46 points located in the area of the water reservoir Poraj. The collected samples were analyzed in terms of content of following elements, which values are in range: total phosphorus (TP) 0.06 – 5.06 g/kg, total nitrogen (TN) 0.17 – 9.66 g/kg, organic matter (OM) 0.49 – 28.41% of solid content, aluminum (Al) 2.44 – 145.15 g/kg and iron (Fe) 0.28 – 16.50 g/kg. By using of GIS system, spatial distribution of obtained results of laboratory analyzes were interpolated (Inverse Distance Weighted method was used). On basis of spatial distribution it was noted that in northern part of water reservoir bottom sediments have greater values of TP, TN and OM than in southern part. The study also included calculation of correlation between: OM and TN (n=46, R² = 0.9335), TN and Fe (n=46, R² = 0.8782), TN and Al (n=46, R² = 0.8629), OM and Fe (n=46, R² = 0.8243), OM and Al (n=46, R² = 0.7981), TP and Fe (n=46, R² = 0.7456), TP and Al (n=46, R² = 0.6209). The presented pilot studies show that the potential content of phosphorus, nitrogen and organic matter in the sediments of the water reservoir Poraj can reach a significant level. The need to plan and carry out further research allowing the evaluation of the properties of the analyzed elements and examining their potential impact on water quality in the tested water reservoir was stated.