DETERMINATION AND SPECIATION OF HEAVY-METALS IN SEDIMENTS OF THE PISUERGA RIVER

We have analysed the contents and speciation of Zn, Cd, Pb, Cu, Ni and Co in sediments taken in the Pisuerga river, that flows through the town of Valladolid and is polluted by industrial and municipal effluents. All heavy metals were determined by voltammetric methods, and their mean total contents were (in μgg-1): Zn, 245.49; Cd, 1.05; Pb, 18.77; Cu, 66.53; Ni, 46.51; and Co, 11.41. We also determined the % H2O, % loss at 800°C, % CaCO3, % organic matter and % organic N for each sediment. All the data were examinated by principal components analysis in order to explain the behaviour of each metal and sampling point. The speciation was carried out by Tessier's method to find five metal categories: (a) adsorptive and exchangeable, (b) bound to carbonates, (c) bound to reducible phases, (d) bound to organic matter and sulphides and (e) residual metals. Cd and Pb, and to a lesser degree Zn, appeared in fractions (a), (b) and (c), whereas Cu, Ni and Co were mainly found in fractions (c) and (d). The residual metal fractions, taken as a guide for pollution, were found to be similar to the ones obtained in rivers belonging to our same European zone. © 1990.