HEAVY METALS DETERMINATION IN GEOCHEMICAL FRACTIONS OF SURFACE SEDIMENT ASSOCIATED WITH MANGROVES IN CIÉNAGA GRANDE DE SANTA MARTA, COLOMBIA

Abstract

The mangrove ecosystem of CGSM has been subjected to strong anthropogenic pressures that have caused changes in the physical and chemical sediment features, among others. Under normal conditions, the sediments associated to the mangroves generate balances that allow the retention of heavy metals in different chemical forms. When the balance is disrupted, metals in the sediment can be mobilized and become available to the biota. In order to estabilsh the mobility and bioavailability potential of Cr, Mn, Ni, Cu, Zn, Cd, As and Pb in surface sediment associated to the mangroves in the CGSM, their contents were analyzed in four areas with different levels of magrove cover. The metals were extracted following the sequential extraction scheme of Tessier and measured by Inductively Coupled Plasma Emission Spectrometry technique (ICP-ES). In general, higher concentrations of the studied metals were found in the non-bioavailable fraction. The metals Mn, Ni, Cu, As, Cd an especially Zn could be potentially mobilized by sediment changes mainly by the oxidation state of sediment; nevertheless, the concentrations of the potentially mobile elements are very low and do not represent environment risks.