Laraque Alain auteur aut IRD Moquet J. S. auteur aut IRD Alkattan R. auteur aut IRD Steiger J. auteur aut IRD Mora A. auteur aut IRD Adèle Georges auteur aut IRD Castellanos B. auteur aut IRD Lagane C. auteur aut IRD Lopez J. L. auteur aut IRD Perez J. auteur aut IRD Rodriguez M. auteur aut IRD Rosales J. auteur aut IRD text journalArticle eng text/pdf born digital access Seasonal variations of total dissolved fluxes of the lower Orinoco River were calculated taking into account four complete hydrological cycles during a five-year period (2005-2010). The modern concentrations of total dissolved solids (TDS) of the Orinoco surface waters were compared with data collected during the second half of the last century published in the literature. This comparison leads to the conclusion that chemical composition did not evolve significantly at least over the last thirty to forty years. Surface waters of the Orinoco at Ciudad Bolivar are between bicarbonated calcic and bicarbonated mixed. In comparison to mean values of concentrations of total dissolved solids (TDS) of world river surface waters (89.2 mg l(-1)), the Orinoco River at Ciudad Bolivar presents mainly low mineralized surface waters (2005-10: TDS 30 mg l(-1)). The TDS fluxes passing at this station in direction to the Atlantic Ocean between 2005 and 2010 were estimated at 30 x 10(6) t yr(-1), i.e. 36 t km(-2) yr(-1). It was observed that the seasonal variations (dry season vs wet season) of total dissolved fluxes (TDS and dissolved organic carbon (DoC)) are mainly controlled by discharge variations. Two groups of elements have been defined from dilution curves and molar ratio diagrams. Ca2+, Mg2+, HCO3-, Cl- and Na+ mainly come from the same geographic and lithologic area, the Andes. K+ and SiO2 essentially come from the Llanos and the Guayana Shield. These findings are important for understanding fundamental geochemical processes within the Orinoco River basin, but also as a baseline study in the perspective of the development of numerous mining activities related with aluminum and steel industries; and the plans of the Venezuelan government to construct new fluvial ports on the lower Orinoco for the transport of hydrocarbons. specialized Hydrochemistry Total dissolved fluxes Hydrology Orinoco River VENEZUELA ZONE TROPICALE ORENOQUE 062 44 SI 4-17 2013 0895-9811 https://www.documentation.ird.fr/hor/fdi:010060396 10.1016/j.jsames.2012.12.011 0895-9811 [F B010060396] https://www.documentation.ird.fr/hor/fdi:010060396 https://www.documentation.ird.fr/intranet/publi/2013/07/010060396.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2013-07-29 2017-08-23 fdi:010060396 fre