Browsing by Autor "Julie Tolu"

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Arsenic, selenium, and mercury speciation in hypersaline lakes of the Andean Altiplano: Link between extreme levels and biodiversity repartition
(Elsevier BV, 2024) Stéphane Guédron; Julie Tolu; David Amouroux; Emmanuel Tessier; Carlos A. Molina; Maı̈té Bueno; Adrien Mestrot; Delphine Tisserand; Darío Achá
Arsenic (As) and mercury (Hg) are highly toxic contaminants whereas selenium (Se) is both an essential trace element and potentially harmful at higher concentrations. The hyper-saline lakes of southern Bolivian Altiplano, which are ecological niches for endemic species, are also expected to be enriched in these toxic trace elements. The biogeochemistry of As, Hg, and Se in such high-altitude extreme environments (e.g., high UV radiation and salt content) remains poorly understood. In this study, we investigated the concentrations and chemical forms (speciation) of As, Hg, and Se in sediment, water, and air samples of Lagunas Colorada (LC), Verde (LV), and Blanca (LB) in the South Lipez region (>4200 m a.s.l.). We compared them with the repartition of biodiversity (invertebrates, algae, and bacteria). Extreme As concentrations were found in water (up to 82 mg L−1), and the main As species was inorganic As(V), with neither biogenic methylated As nor volatile As forms being detected in water and air, respectively. Se concentrations in water were of 0.1 to 1.4 μg L−1, and Se existed under different redox states, i.e., Se(IV), Se(VI), and reduced Se (0, -II), including biogenic methylated Se(-II) (trimethyl selenonium). Volatile Se compounds (e.g., dimethyl selenide) were detected in water and air samples. Hg was enriched in the surface water (6 to 30 ng L−1) compared to other regional water bodies, and a significant amount of methyl-Hg and gaseous Hg(0) was detected. The drastic disparity between As, Se and Hg concentrations and speciation between lakes has important implications for their cycling in these extreme aquatic systems. While As mostly accumulated in its oxidized and non-volatile form, Hg and Se concentrations can be controlled by significant conversion to reduced and methylated forms, allowing efficient evasion to the atmosphere. Finally, the salinity, including major ions, and high levels of As were among the main drivers of biodiversity repartition between lakes.
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
Holocene variations in Lake Titicaca water level and their implications for sociopolitical developments in the central Andes
(National Academy of Sciences, 2023) Stéphane Guédron; Christophe Delaere; Sherilyn C. Fritz; Julie Tolu; Pierre Sabatier; Anne-Lise Devel; Carlos Heredia; Claire Vérin; Eduardo Queiroz Alves; Paul A. Baker
Holocene climate in the high tropical Andes was characterized by both gradual and abrupt changes, which disrupted the hydrological cycle and impacted landscapes and societies. High-resolution paleoenvironmental records are essential to contextualize archaeological data and to evaluate the sociopolitical response of ancient societies to environmental variability. Middle-to-Late Holocene water levels in Lake Titicaca were reevaluated through a transfer function model based on measurements of organic carbon stable isotopes, combined with high-resolution profiles of other geochemical variables and paleoshoreline indicators. Our reconstruction indicates that following a prolonged low stand during the Middle Holocene (4000 to 2400 BCE), lake level rose rapidly ~15 m by 1800 BCE, and then increased another 3 to 6 m in a series of steps, attaining the highest values after ~1600 CE. The largest lake-level increases coincided with major sociopolitical changes reported by archaeologists. In particular, at the end of the Formative Period (500 CE), a major lake-level rise inundated large shoreline areas and forced populations to migrate to higher elevation, likely contributing to the emergence of the Tiwanaku culture.
Late Holocene volcanic and anthropogenic mercury deposition in the western Central Andes (Lake Chungará, Chile)
(Elsevier BV, 2019) Stéphane Guédron; Julie Tolu; Élodie Brisset; Pierre Sabatier; Vincent Perrot; Sylvain Bouchet; Anne‐Lise Develle; Richard Bindler; Daniel Cossa; S. C. Fritz
Late Hololocene mercury deposition history in Lake Chungara (4500 m. a.s.l., Chile): Influence of volcanic eruptions and changes in Paleolimnoecology
(2017) Stéphanie Guédron; Julie Tolu; Élodie Brisset; Pierre Sabatier; Anne‐Lise Develle; Sylvain Bouchet; Richard Bindler; A Dominic; Sherilyn C. Fritz; Paul A. Baker
International audience
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
Reconstructing two millennia of copper and silver metallurgy in the Lake Titicaca region (Bolivia/Peru) using trace metals and lead isotopic composition
(Elsevier BV, 2021) Stéphane Guédron; Julie Tolu; Christophe Delaere; Pierre Sabatier; Julien Barré; Carlos Heredia; Élodie Brisset; Sylvain Campillo; Richard Bindler; Sherilyn C. Fritz