HEAVY-METAL SPECIATION IN COASTAL SEDIMENTS USING TOTAL-REFLECTION X-RAY-FLUORESCENCE SPECTROMETRY

The chemical forms of K, Ca, Ti. Mn, Fe, Ba, Rb, Cr, Cu, Sr, Zn and Pb in the sediments of St. Gilla Lagoon (Sardinia, Italy) are evaluated. Five fractions, consisting of an exchangeable metal fraction, metals bound to carbonates, metals bound to iron and manganese (hydr)oxides, metals bound to organic matter and a fraction of residual metals were separated from sediments by sequential chemical extraction. The metals in each fraction were determined by the total-reflection X-ray fluorescence (TXRF) technique. Both principal and trace element distributions in the sequential phases are discussed in terms of pollution sources, metal transport and deposition/redeposition in air dried sediments.