Chemical composition of kettle holes as an indicator of salinity of small water bodies in northern Poland (the Parsęta catchment, the Borucinka drainage basin)

Kettle holes are commonly found in areas embraced by the last Pleistocene glaciations. They are a natural element of the landscape; together with their closed drainage basins they occupy a large proportion of the area. There are many natural conditions that determine their salinity, those listed most often including alimentation, morphometric features, the dynamics of processes taking place in a drainage basin, paths of water supply, the land-use pattern, agricultural pollution, primary production, and the kind of soil cover. The primary goal of this paper is to determine the level of salinity of kettle holes located in the area of young glacial accumulation on the basis of variations in the chemical composition of their waters. An additional goal is to establish factors, including differences in the hydrographic network and the use and development of land, affecting their salinity. The research was conducted in 6 kettle holes in the Parsęta catchment and in 10 depressions in the Borucinka drainage basin in northern Poland. Laboratory analyses concerned primarily the concentrations of ions determining the hydrogeochemical types of water. The examined kettle holes have lower electrolytic conductance than the water of lakes in the study area. This may be indicative of the dominant role of atmospheric alimentation of their waters. The ions dominating in the chemical composition of water in both drainage basins were HCO3− and Ca2+, with elevated levels of Cl−, Na+, Mg2+, SO42−, and sporadically of K+. The land-use pattern was found to have a significant effect on the level and range of concentrations of the ions under study. The highest average concentrations and their fluctuations were noted in basins located near farms.