Metals in the Scheldt estuary: From environmental concentrations to bioaccumulation

To investigate the relationship between metal concentrations in abiotic compartments and in aquatic species, sediment, suspended matter and several aquatic species (Polychaeta, Oligochaeta, four crustacean species, three mollusc species and eight fish species) were collected during three seasons at six locations along the Scheldt estuary (the Netherlands-Belgium) and analysed on their metal content (Ag, Cd, Co, Cr, Cu, Ni, Pb, Zn and the metalloid As). Sediment and biota tissue concentrations were significantly influenced by sampling location, but not by season. Measurements of Acid Volatile Sulphides (AVS) concentrations in relation to Simultaneously Extracted Metals (SEM) in the sediment suggested that not all metals in the sediment will be bound to sulphides and some metals might be bioavailable. For all metals but zinc, highest concentrations were measured in invertebrate species; Ag and Ni in periwinkle, Cr, Co and Pb in Oligochaete worms and As, Cd and Cu in crabs and shrimp. Highest concentrations of Zn were measured in the kidney of European smelt. In fish, for most of the metals, the concentrations were highest in liver or kidney and lowest in muscle. For Zn however, highest concentrations were measured in the kidney of European smelt. For less than half of the metals significant correlations between sediment metal concentrations and bioaccumulated concentrations were found (liver/hepatopancreas or whole organism). To calculate the possible human health risk by consumption, average and maximum metal concentrations in the muscle tissues were compared to the minimum risk levels (MRLs). Concentrations of As led to the highest risk potential for all consumable species. Cadmium and Cu posed only a risk when consuming the highest contaminated shrimp and shore crabs. Consuming blue mussel could result in a risk for the metals As, Cd and Cr. - Highlights: • This is the first study investigating metal distribution along the aquatic ecosystem of the Scheldt estuary. • Metal concentrations in abiotic and biotic compartments were influenced by sampling location, but not by season. • Metal concentrations in biota decreased from up- to downstream except for arsenic for which an opposite trend was found. • A potential human risk exists when fish or mussels are consumed due to high As values and in some cases due to Cd and/or Cu. - This is the first study that assess the metal concentrations in water, sediment, suspended matter and biota (17 taxa) along the whole Scheldt Estuary covering the whole salinity range from fresh to saline water. This together with the assessment of possible risk for human consumption makes this study unique.