Browsing by Autor "M. Roulet"

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Small-scale Gold Mining in the Puyango River Basin, Southern Ecuador: A Study of Environmental Impacts and Human Exposures
(Lippincott Williams & Wilkins, 2006) Óscar Betancourt; Alfonso Narváez; M. Roulet
P-523 Abstract: Many countries in the world are coming in a complex process of globalization, which will transform the political, environmental, social and economic situation of Latin America countries. Some foreign and native enterprises are working in mining activities in Ecuador, a small country of South America, mainly in small scale gold mining. It is possible that this production system changes to a large scale gold mining in concordance with the globalization process. FUNSAD, a NGO of Ecuador did a study to determine the impact of small-scale gold mining on the environment and communities of the Puyango River basin in the Southwest of Ecuador between 1999 and 2001. Our primary objectives were to measure mercury, manganese and lead in the river, to identify pathways of population exposure, and biological indicators of human exposure. A multi-method design at the catchment scale was applied to the analysis of water, sediments and particulate matter for mercury, lead and manganese over two different seasons. A household survey was undertaken, and individuals were assessed for lead (blood samples), and for mercury (urine and hair samples). River water samples had high concentrations of particulate matter (700 mg/L). Mercury and lead levels in water at the gold processing plants were very high in both seasons (250 ng Hg/L and 160 μg Pb/L). Mercury and lead, there was a downstream gradient with the areas adjacent to the gold processing plants having the highest levels. In Portovelo, the Upper Basin city, 14% of the population reported occupational exposure to inorganic mercury. Although no one in Portovelo consumes water from the river, 10% of the population consumes local fish. This contrasts the Lower Basin where 98% of the population consumes fish, and 100% use river water for drinking and cooking. Lead blood levels over 20 μg/dl were found in 39.4% of the study population and blood mercury over 10ug/L only in 10.0%. Urinary mercury over 4 μg/L was found in 66.5% of the examined persons. Hair methyl mercury did not exceed the safe limit of 2μg/g, the mean concentration was 1.2 μg/g. Mining activity and erosion contributes to heavy metals contamination (mercury, lead and manganese) throughout the Puyango Basin. The relation between environmental contamination is complex and further research is being conducted to understand these relations. Our investigation has produced additional benefits. It has fostered the mobilization of local and national stakeholders of Ecuador to reduce the mining pollution.
Temporal relations between meander deformation, water discharge and sediment fluxes in the floodplain of the Rio Beni (Bolivian Amazonia)
(Wiley, 2006) Erwan Gautier; Daniel Brunstein; Philippe Vauchel; M. Roulet; Oscar Fuertes; Jean‐Loup Guyot; J. Darozzes; L. Bourrel
Abstract The Andean Cordillera and piedmont significantly influence river system and dynamics, being the source of many of the important rivers of the Amazon basin. The Beni River, whose upper sub‐catchments drain the Andean and sub‐Andean ranges, is a major tributary of the Madeira River. This study examines the river in the south‐western Amazonian lowlands of Bolivia, where it develops mobile meanders. Channel migration, meander‐bend morphology and ox‐bow lakes are analysed at different temporal and spatial scales. The first part of this study was undertaken with the aim to link the erosion–deposition processes in the active channel with hydrological events. The quantification of annual erosion and deposition areas shows high inter‐annual and spatial variability. In this study, we investigate the conditions of sediment exportation in the river in relation to three hydrological parameters (flood intensity, date of discharge peak and duration of the bank‐full stage level). The second part of this study, focusing on the abandoned meanders, analyses the cutoff processes and the post‐abandonment evolution during 1967–2001. This approach shows the influence of the active channel behaviour on the sediment diffusion and sequestration of the abandoned meanders and allows us to build a first model of the contemporary floodplain evolution. Copyright © 2006 John Wiley & Sons, Ltd.
Trophic Structure and Bioaccumulation of Mercury in Fish of Three Natural Lakes of the Brazilian Amazon
(Springer Science+Business Media, 2005) D. Sampaio Da Silva; Marc Lucotte; M. Roulet; H. Poirier; Donna Mergler; Elisabeth Oliveira Santos; Marcelo Crossa