Speciation of heavy metals in sediments from salt marshes on the southern Atlantic coast of Spain

A six-step sequential extraction technique was used to determine the chemical association of heavy metals (Pb, Cd, Cu, Fe, Mn, Zn, Cr, Ni) with major sedimentary phases (exchangeable ions, carbonates, manganese oxides, iron oxides, sulfides and organic matter and residual minerals) in samples from salt marshes on the southern Atlantic coast of Spain (Odiel and Bay of Cádiz Salt Marshes). The total metal content was determined as well. In the Bay of Cádiz Salt Marsh sediments, all the metals, except Mn and Pb, were extracted from the residual fraction at a percentage greater than 50%. In the Odiel Salt Marsh, however, only Cr surpasses 50%. The metals that are most easily extractable in the samples analysed were Mn, Zn, Pb and Cd.