Assessment of heavy metal contamination and mineral magnetic characterization of the Asopos River sediments (Central Greece)

[Display omitted] ► Magnetics help to identify compositional alterations of particles across the system. ► Labile metal species accumulate in the estuary. ► Changes in metal speciation in shallow, organic rich estuarine “pools”. ► High energy conditions “remove” occasionally coarse particles to the sea. ► Low energy conditions “remove” regularly very fine particles to the sea. The content and distribution of heavy metals in sediments of the intermittent and contaminated Asopos River, located in Central Greece, was assessed by means of total dissolution, dilute acid and sequential extraction procedures. Mineral magnetic properties were used as proxy parameters of transport mechanisms of land-derived material to the sea. The combination of enrichment factors estimated against local background levels and the levels of labile metals revealed that surface sediments are enriched in Cu, Cd, Ni and Cr. The low flow of the system allows particles and organic matter to accumulate in the estuarine shallow “pools” where they undertake a series of redox reactions, authigenic formation, etc. The most fine of these particles, which are metal rich, are transported to relatively long distances off the Asopos River mouth, even under low energy conditions, converting the system to a secondary source of pollution for the adjacent marine environment.