STUDY OF CHEMICAL SPECIATION IN SEDIMENTS: AN APPROACH TO VERTICAL METALS DISTRIBUTION IN RAPEL RESERVOIR (CHILE)

A sequential chemical extraction method, following a Tessier's protocol has been applied to sample sediment from lake Rapel (34S), an hydroelectric reservoir. This study is a first approach of chemical speciation in this sediment. The four elements determined in the extracts were Cu, Zn, Mn and Fe. Analysis of the extracts was carried out by flame atomic absorption spectrometry (FAAS) and X-Ray fluorescence. The sample sediment was extracted using a core from 1 cm to 40 cm and the level concentration range were: Fe (19850 mg/g - 43899 mg/g), Mn (752 mg/g - 1269 mg/g), Cu (149 mg/g - 478 mg/g) and Zn (224 mg/g - 596 mg/g). Cu was associated to organic matter and carbonate fraction, Zn was associated to oxides Fe-Mn and Fe and Mn were bonding to oxides. All the metals show significant concentration in residual fraction except Cu