The influence of the physicochemical properties of sediment on the content and ecotoxicity of trace elements in bottom sediments.

The sorption mechanisms of the trace elements in bottom sediment are not fully understood. The study aim was to analyse the effect sorption capacity of bottom sediments on the content of trace elements and the bottom sediment ecotoxicity. The study found higher content of trace elements caused higher potential toxicity of bottom sediments. However, the PCA analysis indicated that ecotoxicity to Heterocypris incongruens was not related to the trace element content in the sediments. It was found that some of the physicochemical properties of bottom sediments determine the behavior of the test organism. The study revealed a strong relationships between the properties of bottom sediments and trace element sorption, which results from significant differences in the carbonate and organic matter contents. The obtained relationships showed a significant role in trace element sorption of negatively dissociating functional groups (carboxyl, phenolic, alcohol, and carbonyl groups) of Cha, Cfa, Cnh and DOC fraction and of clay minerals. Positive correlation between the metal content and the volume of ultramicropores, cryptopores and residual pores suggest that these pore groups contain reactive sites capable of effective element sorption. In contrast, larger pores turned out to be of marginal importance in trace elements sorption, probably participating only in their migration within the bottom sediment structure. An understanding of the above factors will provide comprehensive information on the fate of trace elements in aquatic systems.