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(38-32) Geochemical fractionation of metals in the sediments of Cadiz Bay (Spain). Usero, José*,1, Gracia, Ignacio1, Morillo, José1, 1 Universidad de Sevilla, Seville, Spain ABSTRACT- Cadiz Bay is a 10-km-wide inlet located in the southwest of the Spanish Atlantic coast. This bay receives large amounts of pollutant waste such as the residual waters of highly-populated cities and the industrial effluents from companies that use large quantities of metal. As metal sediments are distributed among a variety of physico-chemical forms which exhibit different chemical reactivities, the measurement of the total concentration of a particular metal is not sufficient to determine their possible remobilization. Thus, the chemical form of the metals in the sediment is of great significance in determining their behaviour in the environment. In this study, the distribution of eight metals (Cu, Zn, Cr, Pb, Fe, Ni, Co, Mn) among five phases (exchangeable, bound to carbonates, bound to reducible metal oxides of Fe and Mn, bound to organics and sulphide, and inert fraction) was determined in 10 sediments samples. The results obtained show that there are significant differences in the distribution of the elements analysed in the different phases. The high percentages of Co and Mn in the first and second fractions are significant because the metals in these phases are those with a greater risk of remobilization into water. The element with the highest content in the third fraction is Pb (70 %). Copper is the metal with the highest proportion bound to organics and sulphide (48%), probably due the great tendency for organic matter to complex with it. Finally, the percentage of metal present in the inert fraction is very high for Fe and Cr (93% and 72%, respectively). Key words: sediment, metal pollution, geochemical fractionation |
