ASSESSMENT OF METALS IN SEDIMENTS IN A TRIBUTARY OF GUADALQUIVIR RIVER (SPAIN). HEAVY METAL PARTITIONING AND RELATION BETWEEN THE WATER AND SEDIMENT SYSTEM A. ENGUIX GONZÁLEZ, M. TERNERO RODRíGUEZ, J. C. JIMÉNEZ SÁNCHEZ, A. J. FERNÁNDEZ ESPINOSA and F. J. BARRAGÁN DE LA ROSA ∗ Department of Analytical Chemistry, University of Seville, Avda. Reina Mercedes s/n, E-41012 Seville, Spain ( ∗ author for correspondence, e-mail: fcojose@cica.es) (Received 23 July 1998; accepted 6 August 1999) Abstract. A physical-chemical characterisation of the sediments of the Guadaira River in Southwest Spain has been carried out, determining twenty-three parameters per sample. Non-treated urban sewage and industrial wastewaters from olive oil and table olives affect this river. The factor ana- lysis of the data shows high organic matter contents with metallic pollution. Consequently, points downstream stand out because of very high organic and metallic pollution (Zn, Pb, Cr, Cu and Cd, in order of abundance, showing concentrations in sediments ranging from 50–7500 times those of waters). Heavy metals partitioning studies can be a good approach to show the real activity of these metals in the aquatic environment. We applied Tessier’s analytical sequential extraction scheme to sediments. Sediments would be in general mildly hazardous because we found low levels of easily interchangeable metals in the first fraction. Nevertheless, that is not the case in the river’s last stretch, precisely where sediments are most abundant, the heavy metal levels largest and dredgings are made periodically. Here, their disposal is of concern; since the actual use of these sediments as organic amendment for agricultural soils is unacceptable. Interaction between waters and sediments in the riverbed by means of correlation, factor and cluster analysis on waters and sediments data, was invest- igated. With this approach we concluded that in the final stretch there is a problem of contamination of both, sediments and waters. However, in the middle course only sediments are actually polluted. This corresponds to the previous research, when the situation of waters in this zone was even worse. Keywords: analysis of river sediments, cluster analysis, correlation analysis, factor analysis, Gua- daira River, metal partitioning, water-sediment interaction 1. Introduction Pollution in river waters goes together with pollution of riverbeds, as a consequence of suspended solids sedimentation and fixation over these sediments of various pollutants. Thus, the organic or clay-like sludges that accumulate on the riverbed specially favour fixation to heavy metals, so sediments usually function as a trap, which removes some pollution from waters. In this way, sediment composition can indicate chemical forms that after dumping do not remain soluble in waters. On the other hand, sediments can also act as a contamination source under other conditions, such as the appearance of strong currents, dredgings, the presence of Water, Air, and Soil Pollution 121: 11–29, 2000. © 2000 Kluwer Academic Publishers. Printed in the Netherlands.