Mercury distribution in waters and fishes of the upper Madeira rivers and mercury exposure in riparian Amazonian populations

In this paper, the results of mercury concentrations in two abiotic compartments (river and suspended particles) and two biotic compartments (fish and human hair) from the upper Madeira rivers of the Bolivian Amazon basin are presented. Because of the local hydrological regimes and a high deposition rate in the plain, due to the presence of a subsidence zone at the bottom of the Andean piedmont, in the dry season, the highest mercury concentrations and fluxes were not found in rivers where mining activities took place (2.25-6.99 ng l-1; and 1.07-8.67 mg Hg d-1 km-2), but at the outlet of the Andean basins exploited for their alluvial gold (7.22-8.22 ng l-1; and 9.47-9.52 mg Hg d-1 km-2). The total mercury concentrations measured in surface waters of the upper Beni basin varied during the dry season, from 2.24 to 2.57 ng l-1 in the glacial waters of the Zongo river, to 7.00 ng l-1 in the Madeira River at Porto Velho and 9.49-10.86 ng l-1 at its confluence with the Amazon. The results obtained from fish indicate, on one hand, that 86% of the piscivorous fishes collected in the Beni river were contaminated, and, on the other hand, their high mercury concentrations could exceed by almos four times the WHO (1976) safety limit. (Résumé d'auteur

El mercurio en la amazonia boliviana : sintesis del conocimiento sobre la contaminacion por mercurio en aguas, sedimentos y peces del rio Beni y sus tributarios, impactos sobre las poblaciones riberenas; C 010057498

La contaminacion por mercurio de los rios constituye un problema cada vez mas preocupante en toda la cuenca amazonica. Este mercurio tiene origenes naturales como las emisiones volcanicas o termales, la disolucion de algunas rocas o la erosion de los suelos que, en esta zona del mundo, presentan concentraciones en metales pesados muy elevadas. El mercurio puede provenir tambien de las actividades de explotacion auriferas, cada vez mas numerosas en la Amazonia, region afectada por la "fiebre del oro" nuevamente en los anos 70. (Résumé d'auteur

Hg speciation and stable isotope signatures in human hair as a tracer for dietary and occupational exposure to mercury

Exposure of humans and wildlife to various inorganic and organometallic forms of mercury (Hg) may induce adverse health effects. While human populations in developed countries are mainly exposed to marine fish monomethylmercury (MMHg), this is not necessarily the case for developing countries and diverse indigenous people. Identification of Hg exposure sources from biomonitor media such as urine or hair would be useful in combating exposure. Here we report on the Hg stable isotope signatures and Hg speciation in human hair across different gold miner, indigenous and urban populations in Bolivia and France. We found evidence for both mass-dependent isotope fractionation (MDF) and mass-independent isotope fractionation (MIF) in all hair samples. Three limiting cases of dominant exposure to inorganic Hg (IHg), freshwater fish MMHg, and marine fish MMHg sources are used to define approximate Hg isotope source signatures. Knowing the source signatures, we then estimated Hg exposure sources for the Bolivian gold miner populations. Modeled IHg levels in hair correspond well to measured IHg concentrations (R = 0.9), demonstrating that IHg exposure sources to gold miners can be monitored in hair samples following either its chemical speciation or isotopic composition. Different MMHg and inorganic exposure levels among gold miners appear to correspond to living and working conditions, including proximity to small towns, and artisanal vs large scale mining activity

Cadmium uptake by cocoa trees in agroforestry and monoculture systems under conventional and organic management

Cadmium(Cd) uptake by cocoa has recently attracted attention, after the European Union (EU) decided to establish values for tolerable Cd concentrations in cocoa products. Bean Cd concentrations from some cocoa provenances, especially from Latin America, were found to exceed these values. Cadmium uptake by cocoa is expected not only to depend on a variety of soil factors, but also on plant and management factors. In this study, we investigated the influence of different production systems on Cd uptake by cocoa in a long-term field trial in the Alto Beni Region of Bolivia,where cocoa trees are grown inmonocultures and in agroforestry systems, both under organic and conventional management. Leaf, fruits and roots of two cultivars were sampled fromeach production system alongwith soil samples collected around these trees. Leaf, pod husk and bean samples were analysed for Cd, iron (Fe) and zinc (Zn), the roots for mycorrhizal abundance and the soil samples for ‘total’ and ‘available’ Cd, Fe and Zn as well as DGT available Cd and Zn, pH, organic matter, texture, ‘available’ phosphorus (P) and potassium (K). Only a small part of the variance in bean and pod husk Cd was explained by management, soil and plant factors. Furthermore, the production systems and cultivars alone had no significant influence on leaf Cd. However, we found lower Cd leaf contents in agroforestry systems than in monocultures when analysed in combination with DGT-available soil Cd, cocoa cultivar and soil organic matter. Overall, this model explained 60% of the variance of the leaf Cd concentrations. We explain lower leaf Cd concentrations in agroforestry systems by competition for Cd uptake with other plants. The cultivar effect may be explained by cultivar specific uptake capacities or by a growth effect translating into different uptake rates, as the cultivars were of different size

Geochemistry of the earth's surface meeting

The Titicaca Lake is the most important water resource over the Andean plateau and the ecological equilibrium of this region is nowadays perturbed by recent changes in land use and management practices. The Katari watershed encompasses mining area, cities representing over 1.2 million habitants, and agricultural zones before ending in Cohana bay in the Titicaca Lake. Cohana Bay is known to be one of the most eutrophic bay of the Titicaca Lake. The objective of the study was to evaluate the impact of anthropic activities along the watershed on the river quality and on the bacterial diversity. Both mining activities and release of wastewater in river systems impacts greatly the surface water quality, with level of As exceeding limits for drinking water, and phosphate over the European guidelines for bad quality rivers. Antibiotic from the sulfonamide family was detected in the watershed in high concentrations downstream of the two main cities and bacterial resistance occurred in nearly all the sampled water points

Impacts of Anthropogenic Activities on the Contamination of a Sub Watershed of Lake Titicaca. Are Antibiotics a Concern in the Bolivian Altiplano?

AbstractThe Titicaca Lake is the most important water resource over the Andean plateau and the ecological equilibrium of this region is nowadays perturbed by recent changes in land use and management practices. The Katari watershed encompasses mining area, cities representing over 1.2 million habitants, and agricultural zones before ending in Cohana bay in the Titicaca Lake. Cohana Bay is known to be one of the most eutrophic bay of the Titicaca Lake. The objective of the study was to evaluate the impact of anthropic activities along the watershed on the river quality and on the bacterial diversity. Both mining activities and release of wastewater in river systems impacts greatly the surface water quality, with level of As exceeding limits for drinking water, and phosphate over the European guidelines for bad quality rivers. Antibiotic from the sulfonamide family was detected in the watershed in high concentrations downstream of the two main cities and bacterial resistance occurred in nearly all the sampled water points

How Uncontrolled Urban Expansion Increases the Contamination of the Titicaca Lake Basin (El Alto, La Paz, Bolivia)

International audienc

Metal concentration and bioaccessibility in different particle sizes of dust and aerosols to refine metal exposure assessment

International audienceRefined exposure assessments were realized for children, 7-9yrs, in the mining/smelting city of Oruro, Bolivia. Aerosols (PM>2.5, PM1-2.5, PM0.4-1 and PM0.5) and dust (separated in different particle size fractions: 2000-200μm, 200-50μm, 50-20μm, 20-2μm and <2μm) were sampled on football fields highly frequented by children in both the mining and smelting areas. Trace element concentrations (Ag, As, Cd, Cu, Pb, Sb, Sn and Zn) in each size fraction of dust and aerosols, lung bioaccessibility of metals in aerosols, and gastric bioaccessibility of metals in dust were measured. Exposure was assessed considering actual external exposure (i.e. exposure pathways: metals inhaled and ingested) and simulated internal exposure (i.e., complex estimation using gastric and lung bioaccessibility, deposition and clearance of particles in lungs). Significant differences between external and simulated internal exposure were attributed to dissemblances in gastric and lung bioaccessibilities, as well as metal distribution within particle size range, revealing the importance of both parameters in exposure assessment