Heavy metals in the aquatic environment at the strong conditions of anthropogenic pressure: a case study of Kozłowa Góra Reservoir

Abstract In this article we attempted to investigate the occurrence of metals (Fe, Mn, Zn, Pb, Cu, Cd) in the aquatic environment of the Kozłowa Góra Reservoir (southern Poland) under the influence of the Upper Silesian industry. The reservoir, as a shallow and polymictic unit, has not been the subject of as many extensive studies on the spatial distribution of metals as deep and dimictic reservoirs. The objective of the article is to fill this gap. In our work, we confirmed that the metals in the Kozłowa Góra Reservoir were of anthropogenic origin, and their highest content in the sediments reflected old Brynica riverbed within the reservoir, which transports pollutants from the Silesian agglomeration. The metals detected in the sediments (a fraction f ≥ 0.06 mm) show positive correlations with organic matter. On the other hand, the metals in the fraction f < 0.2 mm had a positive correlation with a silty-clay fraction. During the study, we also found that only Zn, Cd, and Pb in the fraction f < 0.06 mm showed a mean positive correlation with the silty-clay fraction ( f < 0.06 mm). Additionally, we developed the interfacial equilibrium model which allows for the calculation of metal content in the mineral and organic fractions of sediments. The highest concentrations of the analyzed metals occur in the organic fraction, exceeding the concentrations in the mineral fraction by 6 to 34 times. We also developed a model of metal multisorption in the sediment. We found that the accumulation of a given metal in sediment can be influenced by other metals contained in the water and/or sediment. In order to determine the mutual relationships between the metal content in water, in various sediment fractions, and the mass share of the mineral and organic fractions, we developed a cluster analysis method which allows for the isolation of synergistic relationships in the presence of antagonistic relationships. The content of metals in various granulometric fractions of the sediments of the Kozłowa Góra Reservoir we analyzed and showed that metals should be extracted from the fraction f < 0.2 mm, which is the most representative fraction.