Two opposite cases of metal accumulation in ria sediments: Ferrol and Corme-Laxe (Galicia, NW Iberian Peninsula)

Abstract

The accumulation of heavy metals (Cd, Cu, Pb and Zn) in surface sediments (<63 µm) of the Ferrol and Corme-Laxe rias was studied. These two rias have opposite characteristics from the point of view of both the morphology and the anthropogenic impact. Low metal concentrations were found in the Corme-Laxe Ria, with the highest values observed in the Anllóns River estuary, probably due to a higher lithogenic composition of the sediments. Concentrations in the Corme-Laxe Ria (Cd, 0.10 ± 0.03 µg g^–1; Cu, 5 ± 2 µg g^–1; Pb, 12 ± 4 µg g^–1; and Zn, 49 ± 17 µg g^–1) can be used as a good reference for metal background values for sediments from the 18 Galician rias. Although these background values are lower than those previously reported for the Galician coast, they are similar to those found in other uncontaminated coastal and marine systems. The highest concentrations for Ferrol were generally found in the middle part of the ria, which receives the most important urban and industrial impact. The values obtained show evident metal contamination in the middle and inner parts of the Ferrol Ria, with enrichment factors of 4–10 for Cd, 5 for Cu, 2–3 for Pb and 4–5 for Zn.