Assessment of microscale variation of heavy metal pollution of the Bystrzyca river alluvia downstream from Lublin

Fluvial sediments accumulated in the bottoms of river valleys downstream from large cities are characterised by higher levels of heavy metal content, which poses a threat to the environment and humans. This study presents a comprehensive assessment of the degree of pollution of four alluvial sediment profiles (80 samples), collected from the bottom of the Bystrzyca river valley downstream from Lublin, conducted with the use of five geochemical indices. Channel deposits and sediments (alluvial soils) sampled from the floodplain were analysed. The content levels of the six heavy metals under study were as follows: Cd: 10.6–291.2 mg/kg, Cr: 53.1–292.4 mg/kg, Cu: 20.4–223.1 mg/kg, Ni: 2.9–19.3, Pb: 39.3–280.3, Zn: 108.9–991.4 mg/kg. The horizontal and vertical variation of the pollution level was linked with the history of anthropogenic pressure on the one hand, and the geomorphological location of a given profile on the other. Heavy metal content in the samples did not show any correlation with grain size composition, organic matter content, and Fe and Mn content. Cadmium was the element whose concentration levels were comparable with those in alluvial sediments of rivers in industrialised areas while the indices for the other metals showed varied levels of pollution: from low to high. However, the ecological risk is high for all samples as indicated by the synthetic potential ecological risk index, which takes into account the toxicity of all the metals under study.