Geochemistry of Major and Trace Elements in Sediments of the Ria de Vigo (NW Spain): an Assessment of Metal Pollution

Ria de Vigo is a funnel-shaped, fault-bounded coastal embayment in Galicia, NW Spain. There are a number of important centres of population and industrial activity along its margins, which serve as sources of pollution. Sixty-six subtidal sediment samples have been collected in the Ria. The samples have been subjected to a total digestion technique and analysed for major and trace elements (Al, Fe,Ti, Mn, Cu, Pb, Cr, Zn, Co, As, Ni, Cd and Sr). Variations of absolute metal concentrations reflected variations in textural and/or carbonate and organic matter content. Geoaccumulation indexes and enrichment factors have been calculated to assess whether the concentrations observed represent background or contaminated levels. It is proved that the choice of the background plays an important role in the interpretation of the geochemical data. PCA was a very useful tool to define background values for metals in the Ria de Vigo area. These values were similar to regional values given by other authors. It is concluded that the Ria is slightly to moderately polluted for some of the studied metals. The spatial extent of pollution was examined, and it was found that the most polluted area is located in the inner and southern parts of the Ria.