This work has been developed with the aim of determining the environmental quality of the sediments in
the Guadiana river estuary, and evaluating the possible incidence that some processes associated to human
activities (acid mine drainage, urban effluents) could produce in this sediments. For this purpose, the
geochemical and granulometric characterization of the estuary sediments have been determined, and the
enrichment factors have been calculated for the most important metals and metalloids (As, Cd, Co, Cr,
Cu, Fe, Mn, Ni, Pb and Zn).The results obtained evidences a distribution of the metals and metalloids in
two groups: Group I with elements with a natural origin ( Al, Fe, Mn, Co, Cr and Ni ), and Group II, with
elements associated to an anthropic origin ( As, Cd, Cu, Pb and Zn ). The enrichment factors for the
elements of the Group II, are indicative of the existence of a diffuse mining contamination, associated with
the acid mine drainage of internal zones of the basin. There has been also found out anomalous
concentrations of some of these elements near the villages of Ayamonte and Villa Real de Sto Antonio