Abstract
The distribution of six common metal contaminants (Cd, Cr, Cu, Ni, Pb, Zn) in the bulk (<2 mm) and fine fractions (<63 µm) of freshwater sediments was compared to conclude on the long-existing dilemma which fraction should be used in the investigation of the metal contamination. The environments included in the study (24 rivers, 8 lakes) were very different with respect to sediments origin and composition and they provided a good review of the possible scenarios. For the river sediments, particularly those having >40% of sand fraction, metal concentrations were up to seven times higher in the fine fraction, implying the necessity for considering sand dilution effect in compositional data analysis. The same samples were also characterized with higher organic matter content (OM) in the fine fraction. Lake environments were characterized by fine-grained sedimentation and the difference between metal concentrations in the bulk and fine fraction was not so expressed. The preparation of samples for the geochemical and compositional data mining should be carried out in accordance with the sedimentological characteristics of the investigated environment. It implies that the insight into geological setting and determination of sedimentological characteristics should be an obligatory part of monitoring/investigating metal contamination in freshwater sediments. For river sediments, the analysis of the fine sediment fraction or correction for sediment lithology are advisable.
Highlights
In an attempt to add some new insight in the matter, this study is aimed at: (1) Investigating the distribution of selected heavy metals (Cd, Cr, Cu, Ni, Pb, and Zn) in the bulk (
Some of the fine-grained material may be flocculated [23] and attributed to the sand fraction since no chemical agent or physical force was applied during the wet sieving of the sediment samples
The samples containing >60% of sand fraction, those from the river environments, had up to seven times higher concentrations of metals in the fine fraction than in the bulk sediment, but a significant difference was noticed for all samples containing more than 40% of sand
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Mineral particles in freshwater environments are transported downstream by the river flow depending on the particle size and intensity of the river discharge. Coarser particles tend to be more stationary while fine material is resuspended and displaced. The particle size distribution (PSD) of river sediments is quite variable
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