Sondag Francis auteur aut IRD Guyot Jean-Loup auteur aut IRD Moquet J.S. auteur aut IRD Laraque Alain auteur aut IRD Adèle Georges auteur aut IRD Cochonneau Gérard auteur aut IRD Doudou Jean-Claude auteur aut IRD Lagane Christelle auteur aut IRD Vauchel Philippe auteur aut IRD text journalArticle eng text/pdf born digital access This study presents the data collected within the framework of an Observatory of Research in Environment on the Amazonian Basin-the ORE HYBAM. It relates to the dissolved and solid loads of the two main rivers of French Guiana, the Maroni and Oyapock rivers, running on the Guiana Shield and draining respectively 64 230 and 24 630 km(2). The low coefficient of variation of the average annual flows of the two rivers indicates an inter-annual hydrological stability probably related to the immediate vicinity of the Atlantic Ocean. The sedimentary load is mainly composed of quartz and kaolinite. The total suspended solid (TSS) concentrations are among the world's lowest values; they range from 1 to 130 mg l(-1) during the hydrological cycle, with averages of 22 and 12 mg l(-1), for the Maroni and Oyapock rivers, respectively. The seasonal variability of these values is significantly higher than that of hydrologic flows, but without simple relationship with the discharge. Water chemical composition of the two rivers indicates a very weak mineralization, very similar to that found in the Amazonian rivers running on the Brazilian and Guianese shields, and in the Congo River and its tributaries in the Central African Shield. Seasonal variations are observed in both basins; they correspond to higher concentrations during low water stage (from October to February) and to more diluted water during the flood, from April to July. A signature enriched in Cl- is present at the Saut Maripa station on the Oyapock River indicating a more marked influence of the trade winds in this basin. The computation of atmospheric contributions to ions budget indicated a weak contribution for Ca2+ and Mg2+, which originates mainly from water-rock interactions in both stations, while more than half of Na+ is derived from atmospheric inputs. specialized hydrology suspended sediment geochemistry French Guiana Amazon region 062 24 11 1433-1445 2010 0885-6087 https://www.documentation.ird.fr/hor/fdi:010049503 10.1002/hyp.7603 0885-6087 [F B010049503] https://www.documentation.ird.fr/hor/fdi:010049503 https://www.documentation.ird.fr/intranet/publi/2010/05/010049503.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2010-06-02 2017-08-23 fdi:010049503 fre