This main aim of this work is the determination of the regional background in Holocene sediments of the
Guadiana River estuary. These background values are essential in order to establish the environmental
quality of the most recent sediments, and to evaluate the possible incidence that some processes associated
to human activities (acid mine drainage, urban effluents) could produce in these sediments. For this purpose,
a sedimentological and geochemical characterization have been done in two sediment cores from the
lower Guadiana basin, in which Al normalized concentration has been calculated for the most important
metals and metalloids present in these sediments (As, Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb and Zn).The results
obtained have allowed us the determination of the regional background in these sediments