Lead and Zinc contamination of surface sediments in the main harbours of the Galician Rias

Abstract

The concentration ranges and degree of contamination of lead and zinc in the four principal harbour areas of the northwest Iberian Peninsula have been defined from 130 surface sediment samples (<63 μm fraction) using the pre-industrial background equations obtained from metal analysis of four sediment cores. The increase of metals may be associated with the ria-harbour areas: (a) for lead to values of 140 mg·kg-1 in Pontevedra, 160 mg·kg-1 in Ferrol and Coruña and 320 mg·kg-1 in Vigo; (b) for zinc to values of 150 mg·kg-1 in Pontevedra, 380 mg·kg-1 in Coruña, 600 mg·kg-1 in Ferrol and 1960 mg·kg-1 in Vigo. The areal distribution patterns of lead and zinc in sediments, with higher concentrations at locations close to the metal sources, reflect firstly the influence of harbour activities and secondly the shipyard works in the rias. The degree of lead and zinc contamination in these harbour sediments, based on the calculation of normalized factors of sediment enrichment, can be defined as moderate to considerable in the harbours of La Coruña and Pontevedra and severe in Ferrol and Vigo. In other parts of the rias the contamination usually decreases, as is generally observed for other world estuaries or coastal zones where there are harbours.