Aucour A.M. auteur aut IRD Tao F.X. auteur aut IRD Moreira Turcq Patricia auteur aut IRD Seyler Patrick auteur aut IRD Sheppard S. auteur aut IRD Benedetti M.F. auteur aut IRD text journalArticle eng text/pdf born digital access We studied the changes in major elements and organic carbon concentrations during the initial stage of the mixing of the black (Rio Negro) and the White (Rio Solimoes) waters in the Amazon River basin to understand the geochemical processes that could control the redistribution between particulate and dissolved fractions. Water samples were collected at six stations including the Rio Negro and the Rio Solimoes and four stations downstream from the confluence. The relative contributions of the two tributaries were determined using a triple tracer approach (delta(18)O, deltaD, Cl-). Particulate (>0.2 mum) and dissolved ( <0.2 mum) concentrations of major elements (Ca, Mg, Fe, Al, Si) and organic carbon (POC and DOC) were measured. Major elements in the particulate fraction were found to have a nonconservative behaviour in the initial stage of the mixing due to mineral removal. In the dissolved fraction, only the DOC, Fe, and Mn behaved nonconservatively. The Fe losses could be due to preferential removal of Fe bound to N-rich organic matter (OM) and/or to preferential removal of Fe oxyhydroxides. The increasing dissolved manganese content in the dissolved phase is explained by a reductive dissolution of manganese oxides due to massive inputs of phenolic-rich OM from the Rio Negro. The amount of DOC removed from the water column in the initial stage of the mixing would represent 4% of the total annual DOC flux of the Amazon River at the reference gauging station of Obidos. specialized COURS D'EAU TRANSPORT SOLIDE ELEMENT CHIMIQUE MAJEUR ELEMENT EN TRACE METAL ION FER ALUMINIUM MANGANESE MATIERE ORGANIQUE DISSOUTE MATIERE ORGANIQUE PARTICULEE MATIERE EN SUSPENSION SEDIMENT CARBONE ORGANIQUE ANALYSE CHIMIQUE ANALYSE ISOTOPIQUE GEOCHIMIE CHIMIE DE L'EAU AMAZONIE 062MECEAU04 197 1-4 271-285 2003 0009-2541 https://www.documentation.ird.fr/hor/fdi:010031308 10.1016/S0009-2541(02)00398-4 0009-2541 [F B010031308] https://www.documentation.ird.fr/hor/fdi:010031308 https://www.documentation.ird.fr/intranet/publi/depot/2015-09-11/010031308.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2003-09-25 2015-11-09 fdi:010031308 fre