J. Phys. IV France 107 (2003) 119
How plants of the Amazonian floodplain (Brazil) can affect the geochemical status of trace elements in the Amazon River mainstream?G. Barroux1, J. Viers1, P. Seyler1, P. Oliva1, B. Dupré1, J.-L. Guyot1 and M. Pinelli2
1 LMTG, CNRS/ IRD, Université Paul Sabatier, 38 rue des 36 Ponts, 31400 Toulouse, France
2 instituto de Geociéncias, Universidade de Brasilia, Campus Universitario Darcy Ribeiro, ICC-Central, CEP 70910-900 Brasilia, Brazil
Multi-element analysis of plant tissue samples increased this last 20 years, in relation to chemical weathering processes. However, if plants play a key role in terms of storage and transfer of elements (major and trace) in natural ecosystems, our knowledge of transfer processes and fluxes are still poor. In the present study, we measured the concentrations of major and trace elements in the leaves of four different species (annual and perennial) of an amazonian floodplain during one hydrological period. The studied site is the "Ilha de Marchantaria" (3°15'S; 60°00'W) located on the Solimões River (Upper Amazon), near the city of Manaus. The results reveal high concentrations (from 10 to 1000 ppm for Al, Mn and Fe; from 10 to 100 ppm for Rb, Sr and Ba) in leaves and an annual variation wich is reverse of the river discharge (High concentrations for low water level and low concentrations for high water level). According with datas of net primary production (100 t.ha -1y -1) and of total floodplain area (200000 km 2), we estimate the amount of trace elements stored or recycled in the vegetation of the amazon floodplains. We also observed that the amount of trace metals exported by the amazon  is one hundred time less than the amount of trace metals stored or recycled by the vegetation.
© EDP Sciences 2003