J. Phys. IV France
Volume 107, May 2003
Page(s) 1213 - 1218

J. Phys. IV France
107 (2003) 1213
DOI: 10.1051/jp4:20030519

A first quantitative estimate of trace metal fluxes from Amazon river and its main tributaries

P.T. Seyler1, M. Pinelli2 and G.R. Boaventura2

1  LMTG-IRD, UMR 5563, Université Paul Sabatier, 38 rue des 36 Ponts, 31400 Toulouse, France
2  Instituto de Geociências, Universidade de Brasilia, 70910-900 Brasilia, Brazil

The trace metal (V, Cr, Mn, Co, Cu, Zn, As, Rb, Sr, Mo, Cd, Sb, Cs, Ba, U) concentrations and temporal variabilities of the Amazon river and its main tributaries are studied on time series basis in the major tributaries of Amazon river (Negro, Madeira and Solimões Rivers) and at Obidos station on the Amazon mainsteem which represents 90% of the total discharge of Amazon river to the Ocean. Variations of river chemistry may reflect variations of the sources. The "Shield" rivers (as the Rio Negro) have typically depleted concentrations in As, Sr, Ba, Cu, and V as compared with Andean rivers. Elements such Mn and As are mainly transported by the flood flows. These elements are known to be concentrated in lateric (ferricrete) soils which represent 80% in the Amazon basin, suggesting that these elements are washed away in solution during the high discharge. Moreover, these elements can be stored in the surrounding floodplain areas (varzea) where deposition/resuspension cycles as well as the exchange rate between floodplain and mainstream channel may control at least partially the temporal variation of redox element concentrations such Mn and As. Implication on these results on the trace element flux from Amazon River to the Atlantic Ocean is discussed.

© EDP Sciences 2003