Browsing by Autor "Marc Roulet"

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Channel and floodplain sediment dynamics in a reach of the tropical meandering Rio Beni (Bolivian Amazonia)
(Wiley, 2010) Erwan Gautier; Daniel Brunstein; Philippe Vauchel; Jean‐Marie Jouanneau; Marc Roulet; Coral García; Jean‐Loup Guyot; Marcello Castro
Abstract The study investigates interactions, water and sediment exchanges, between a rapidly migrating meander and its associated floodplain at fine temporal and spatial scales. The Beni River, an Amazonian free meandering river, makes the transition between Andean ranges and Amazonian lowlands. For the period 2002–2006, an assemblage of tools and methods (water and sediment discharges, topometric and bathymetric surveys, sedimentation rate estimations from unsupported 210 Pb and sediment trapping system) was used to jointly analyse the influence on the sediment budget of external factors (mainly water and sediment discharge) and the inherent behaviour of the system. The main issue addressed is the investigation of the complex relationship between ‘morphological conditioning’ of fluvial landform and process. The first part of the study was undertaken with the aim of linking erosion–deposition in an active meander with water and sediment fluxes. The three inter‐annual evolutions are characterized by very unequal sediment budgets; the first two intervals underwent predominant erosion, and the latter slight accumulation. Digital elevation models, evaluated for the active meander, demonstrate that sedimentation on the point bar depends more on external factors than erosion of the concave bank, which fluctuates slightly. The second part of the study, focusing on water and sediment exchanges between active bend and floodplain, examines the respective parts played by overbank flow and by an abandoned channel on the diffusion and sequestration of sediment. The association of short‐ and long‐term estimation of sedimentation rates suggests that floodplain construction is associated with two different processes and rhythms of sediment transportation. Finally, a sediment budget is proposed for the Beni River in the upper part of the Amazonian lowlands. Copyright © 2010 John Wiley & Sons, Ltd.
Contamination of surface waters by mining wastes in the Milluni Valley (Cordillera Real, Bolivia): Mineralogical and hydrological influences
(Elsevier BV, 2008) Matías Miguel Salvarredy-Aranguren; Anne Probst; Marc Roulet; Marie‐Pierre Isaure
Evidencias sedimentarias y geoquimicas de la pequeño edad de hielo en el lago milluni grande del altiplano boliviano
(Centre National de la Recherche Scientifique, 2009) Matías Miguel Salvarredy-Aranguren; Anne Probst; Marc Roulet
International audience
Macroinvertebrate food web structure in a floodplain lake of the Bolivian Amazon
(Springer Science+Business Media, 2010) Carlos I. Molina; François‐Marie Gibon; Thierry Oberdorff; Eduardo Domı́nguez; Julio Pinto; Rubén Marín; Marc Roulet
Small-scale Gold Mining in the Puyango River Basin,Southern Ecuador: A Study of Environmental Impacts andHuman Exposures
(Springer Science+Business Media, 2005) Óscar Betancourt; Juan Alberto Narváez Olalla; Marc Roulet
Sulfate-Reducing Bacteria in Floating Macrophyte Rhizospheres from an Amazonian Floodplain Lake in Bolivia and Their Association with Hg Methylation
(American Society for Microbiology, 2005) Darío Achá; Volga Iñiguez; Marc Roulet; Jean Remy Davée Guimarães; Ruddy Luna; L. Alanoca; Samanta Sánchez
Five subgroups of sulfate-reducing bacteria (SRB) were detected by PCR in three macrophyte rhizospheres (Polygonum densiflorum, Hymenachne donacifolia, and Ludwigia helminthorriza) and three subgroups in Eichhornia crassipes from La Granja, a floodplain lake from the upper Madeira basin. The SRB community varied according to the macrophyte species but with different degrees of association with their roots. The rhizosphere of the C4 plant Polygonum densiflorum had higher frequencies of SRB subgroups as well as higher mercury methylation potentials (27.5 to 36.1%) and carbon (16.06 +/- 5.40%), nitrogen (2.03 +/- 0.64%), Hg (94.50 +/- 6.86 ng Hg g(-1)), and methylmercury (8.25 +/- 1.45 ng Hg g(-1)) contents than the rhizosphere of the C3 plant Eichhornia crassipes. Mercury methylation in Polygonum densiflorum and Eichhornia crassipes was reduced when SRB metabolism was inhibited by sodium molybdate.
Transfer of mercury and methylmercury along macroinvertebrate food chains in a floodplain lake of the Beni River, Bolivian Amazonia
(Elsevier BV, 2010) Carlos I. Molina; François‐Marie Gibon; Jean-Louis Duprey; Eduardo Domı́nguez; Jean-Remy D. Guimarães; Marc Roulet