PHYSICOCHEMICAL SPECIATION OF TRACE-ELEMENTS IN RIVER WATERS BY SIZE FRACTIONATION

Size fractionation method has been used for the speciation of trace elements in river waters. Both filtration and ultrafiltration techniques were applied to fractionate the trace elements into various sizes and/or molecular weight ranges. The size distribution was determined for 39 elements by means of neutron activation analysis to estimate their physicochemical forms. Alkali and alkaline earth elements, heavy rare earth elements (REEs), As, Co, Mn, Ni, Sb, Se, V, W, and Zn were mainly present in the dissolved phase, while Ag, Al, Fe, Sc, and light REEs were predominantly associated with the suspended particles. The dominant dissolved species for alkali and alkaline earth elements, Al, V, Mn, Sb, and Au were regarded as simple ions, while heavy REEs, Sc, Co, Ni, and Zn were apt to form soluble complexes with organic ligands. Light REEs, Fe, and Ag were mainly associated with colloidal materials.