Metal concentration in sediments samples from two vibracores in the Tinto river estuary it has been
determined. The enrichment factors (EF) of metal associated to sulphide deposits (Fe, Cu, Zn, Pb and As),
in most cases, is over 2. Cu, Zn and As have much higher EF, over 10 in surficial samples. The progressive
shallowness of the estuary has undergone a relative increase in acidic river water volume with respect to
seawater. This effect has originated a downstream displacement of acid mixing processes affecting the
estuary, which is reflected in higher metal concentration in sediments of the outer zones of the system