Changes in the Concentration of Selected Metals in Sediments of the River Chotla in Northwest Poland in Its Section Affected by Various Anthropogenic Factors

The purpose of the paper was to assess the changes in the concentration of selected metals in the bottom sediment and interstitial water of the River Chotla in northwest Poland. The research was conducted on the river section flowing through Zaspy Małe and a salmonid fish breeding farm. Samples of water and bottom sediment were taken in four control and measurement points, located above and below the village and on a backwater above the trouteries and below the fish breeding ponds. The pH and the concentration of the metals potassium, iron, calcium, manganese and zinc were determined in the water and sediment samples. The lowest concentrations of the metals were found in the samples collected above and below Zaspy Małe, while the highest concentrations of metals in the water and sediment were found in the samples taken in the backwater, above the fish breeding ponds. Exceptions were calcium and potassium, with the highest concentrations of metals in the water being found in the samples taken below the fish breeding ponds. The content of metals in sediments of the analysed section of the River Chotla was mainly determined by the content of organic matter, which varied as it is dependent on water accumulation processes and the operation of nearby fishery facilities. The slightly alkaline pH facilitated long-lasting accumulation of metals in sediments.