Browsing by Autor "Sarah Bureau"

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Accumulation of Methylmercury in the High-Altitude Lake Uru Uru (3686 m a.s.l, Bolivia) Controlled by Sediment Efflux and Photodegradation
(Multidisciplinary Digital Publishing Institute, 2020) Stéphane Guédron; Darío Achá; Sylvain Bouchet; David Point; Emmanuel Tessier; Carlos Heredia; Stéfany Rocha-Lupa; Pablo Fernandez-Saavedra; Marizol Giovana Flores; Sarah Bureau
In shallow aquatic environments, sediment is a significant source of monomethylmercury (MMHg) for surface water (SW). High-altitude aquatic ecosystems are characterized by extreme hydro-climatic constraints (e.g., low oxygen and high UV radiation). We studied, during two seasons, the diel cycles of MMHg in SW and sediment porewaters (PW) of Lake Uru Uru (3686 m a.s.l, Bolivia) contaminated by urban and mining activities. Our results show that diel changes in SW MMHg concentrations (up to 1.8 ng L−1) overwhelm seasonal ones, with higher MMHg accumulation during the night-time and the dry season. The calculation of MMHg diffusive fluxes demonstrates that the sediment compartment was the primary source of MMHg to the SW. Most MMHg efflux occurred during the dry season (35.7 ± 17.4 ng m−2 day−1), when the lake was relatively shallow, more eutrophicated, and with the redoxcline located above the sediment–water interface (SWI). Changes in MMHg accumulation in the PWs were attributed to diel redox oscillations around the SWI driving both the bacterial sulfate reduction and bio-methylation. Finally, we highlight that although MMHg loading from the PW to the SW is large, MMHg photodegradation and demethylation by microorganisms control the net MMHg accumulation in the water column.
Corrigendum to “Pre-hispanic wetland irrigation and metallurgy in the South Andean Altiplano (Intersalar Region, Bolivia, XIVth and XVth century CE)” [Quat. Sci. Reviews 338 (2024) 108826]
(Elsevier BV, 2025) Stéphane Guédron; Clément Roy; Géraldine Sarret; Julie Tolu; Marie‐Pierre Ledru; Sylvain Campillo; Sarah Bureau; Anne‐Lise Develle; Charline Guiguet-Covex; Eduardo Queiroz Alves
Extreme Arsenic Bioaccumulation Factor Variability in Lake Titicaca, Bolivia
(Nature Portfolio, 2019) Géraldine Sarret; Stéphane Guédron; Darío Achá; Sarah Bureau; Florent Arnaud‐Godet; Delphine Tisserand; Marisol Goñi‐Urriza; Claire Gassie; Céline Duwig; Olivier Proux
Latin America, like other areas in the world, is faced with the problem of high arsenic (As) background in surface and groundwater, with impacts on human health. We studied As biogeochemical cycling by periphyton in Lake Titicaca and the mine-impacted Lake Uru Uru. As concentration was measured in water, sediment, totora plants (Schoenoplectus californicus) and periphyton growing on stems, and As speciation was determined by X-ray absorption spectroscopy in bulk and EDTA-extracted periphyton. Dissolved arsenic was between 5.0 and 15 μg L-1 in Lake Titicaca and reached 78.5 μg L-1 in Lake Uru Uru. As accumulation in periphyton was highly variable. We report the highest As bioaccumulation factors ever measured (BAFsperiphyton up to 245,000) in one zone of Lake Titicaca, with As present as As(V) and monomethyl-As (MMA(V)). Non-accumulating periphyton found in the other sites presented BAFsperiphyton between 1281 and 11,962, with As present as As(III), As(V) and arsenosugars. DNA analysis evidenced several taxa possibly related to this phenomenon. Further screening of bacterial and algal isolates would be necessary to identify the organism(s) responsible for As hyperaccumulation. Impacts on the ecosystem and human health appear limited, but such organisms or consortia would be of great interest for the treatment of As contaminated water.
Pre-hispanic wetland irrigation and metallurgy in the South Andean Altiplano (Intersalar Region, Bolivia, XIVth and XVth century CE)
(Elsevier BV, 2024) Stéphane Guédron; Clément Roy; Géraldine Sarret; Julie Tolu; Marie‐Pierre Ledru; Sylvain Campillo; Sarah Bureau; Anne‐Lise Develle; Charline Guiguet-Covex; Eduardo Queiroz Alves