Study of metal bioaccumulation by nuclear microprobe analysis of algae fossils and living algae cells

Microscopic ion-beam analysis of palaeo-algae fossils and living green alga e cells have been performed to study the metal bioaccumulation processes. T he algae fossils, both single cellular and multicellular, are from the late Neo-proterozonic (570 million years ago) ocean and perfectly preserved wit hin a phosphorite formation. The biosorption of the rare earth element ions Nd3+ by the green algae species euglena gracilis was investigated with a c omparison between the normal cells and immobilized ones. The new Leipzig Na noprobe, LIPSION, was used to produce a proton beam with 2 mu m size and 0. 5 nA beam current for this study. PIXE and RES techniques were used for ana lysis and imaging. The observation of small metal rich spores (< 10 mu m) s urrounding both of the fossils and the living cells proved the existence of some specific receptor sites which bind metal carrier ligands at the micro bic surface. The bioaccumulation efficiency of neodymium by the algae cells was 10 times higher for immobilized algae cells. It confirms the fact that the algae immobilization is an useful technique to improve its metal bioac cumulation. (C) 2000 Elsevier Science B.V. All rights reserved.