Metals in sediments of the Sado estuary, Portugal

Surface sediments were collected from 50 stations all over the Sado estuary and analysed for Al, Si, Ca, Mg, Fe, Mn, Zn, Cu, Cd, Pb, Cr, Ni, Co and Ag. The element/Al ratios showed considerable variations along the estuary, mainly as a result of different sediment origins and metal anthropogenic inputs. Principal component analysis applied to those ratios demonstrated that Cu, Fe, Pb, Cr, Co and Ni were more closely associated with sediments deposited near the industrial area, while Cd, Zn and Mn to those in the upper limit of the estuary. Correlations among the metal/Al ratios reflect the major sources of the metals.