Essential and non-essential metals in three lowland rivers of temperate South America (Argentina): Distribution and accumulation.

Background: Geographic distribution of essential metals on earth is largely uneven. Therefore, regional specific approaches to assess metal contents in freshwater ecosystems are mandatory. Cd, Cu, Cr, Pb, Ni, Mn and Zn concentrations were measured in water, sediments and fish tocharacterize the partitioning of these essential and non-essential metals in three river ecosystems of the Pampean Plain==.

Methods: Water, sediment and eight fish species were collected at three rivers from the Pampean Plain. After sample-specific pretreatments, Cd, Cr, Cu, Mn, Ni, Pb and Zn concentrations in water, sediment and muscle were determined in triplicate by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). Contamination (Hakanson´s index) and bioconcentration factors were calculated to assess the degree of contamination and the relationship between the matrices, while the target hazard quotient was estimated to explore the risk to human health from fish consumption.

Results: Water metal concentration was below detection limit in all sampled rivers. Sediments were mostly enriched by Mn (186-474 mg kg) followed by Zn (36.8-40.3 mg kg), whereas in fish, the situation was the opposite, suggesting different biogeochemical pathways and uneven bioaccumulation of these elements. The largest concentrations for all explored metals were invariably recorded in fish from the Sauce Grande River, although only Cd, Cu and Ni in sediments were highest at this site. Indeed, the bioconcentration factor showed that Cd and Zn are actively accumulated by almost all species in all sampled rivers. The Targeted Hazard Quotient based on the muscle metal concentration tissue of the edible fish species (Odontesthes bonariensis) was less than 1.

Conclusion: None metal seemed to pose a significant risk for humans. In some sites biota-sediment concentration factors of Cd and Zn and muscle Cd, Cr, Ni, Zn and Pb levels were highest in the silurid Pimelodella laticeps, suggesting that it may be used as a sentinel species for biomonitoring programs in Neotropical fish assemblages.