Jean-Sébastien Moquet

• PhD
• PostDoc Position at Institut des Sciences de la Terre d'Orléans

Knowledge of the age of organic carbon (C) that is leached from soils to streams is key to understanding how C is mobilised within ecosystems. The tropics are characterised by significant C fluxes through streams, yet the time scales of organic C sequestration and export remain uncertain in these regions. Here we examined the concentration, composi...

Bullet points 21 • The Ogooué River catchment is denuding at a low rate (38 t/km 2 /a, 15 m/Ma) 22 • There is substantial chemical denudation: > 30% of the total denudation 23 • Batéké Px not producing solutes because constituted by already weathered material 24 • The southern part of the catchment is denuding twice as fast as the northern part 25...

Despite covering only 3% of the global land surface, peatlands are an active part of the Critical Zone (CZ) exchanging large water and greenhouse gas (GHG) fluxes with the surrounding aquifers, surface waters, and the atmosphere. While ecosystem services of peatlands (carbon and water storage, buffering of local climate) are essential to address 21...

Peatlands cover only 3 % of emerged lands, but their carbon stock represents about 30 % of the global soil organic carbon. Climate change and local anthropogenic disturbances deeply affect the hydrological functioning of peatlands. This may trigger carbon fluxes to surface waters and the atmosphere, thus leading to a positive feedback for global wa...

Continental hydrosystems and in particular peatlands play an important role in the carbon cycle of the Critical Zone (CZ). Peatlands are important sinks for organic carbon and have therefore been extensively studied. However, peatlands are not only important for the fate of organic carbon, but they also affect the cycle of Dissolved Inorganic Carbo...

The infiltration of organic-rich surface waters towards groundwaters, is known to play a significant role in carbonate weathering and in contributing to the atmospheric continental carbon sink. This paper investigated biogeochemical interactions in karst critical zones, with strong surface water /groundwater interactions, and in particular the role...

From water rock-interaction to methanogenesis: How climate induced raise of groundwater inputs might favor CH4 fluxes in the mid latitude/altitude Frasne peatland, Jura Mountains, France. Abstract Peatlands are socio-ecosystems that constitute an inherent part of the Critical Zone in which water quality and quantity are key components of biogeochem...

Mitigating and adapting to global changes requires a better understanding of the response of the Biosphere to these environmental variations. Human disturbances and their effects act in the long term (decades to centuries) and consequently, a similar time frame is needed to fully understand the hydrological and biogeochemical functioning of a natur...

The Tropical Atlantic is facing a massive proliferation of Sargassum since 2011, with severe environmental and socioeconomic impacts. As a contribution to this proliferation, an increase in nutrient inputs from the tropical rivers, in response to climate and land use changes or increasing urbanization, has been often suggested and widely reported i...

Due to the many factors controlling δ¹³C values in stalagmites, complicating their paleoclimatic and paleoenvironmental interpretation, most studies do not present δ¹³C values, but instead focus mainly on δ18O values. This is also the case for most cave studies from tropical South America, where many new δ18O stalagmite records covering the last mi...

Despite the absence of tectonic activity, cratonic environments are characterized by strongly variable, and in places significant, rock weathering rates. This is shown here through an exploration of the weathering rates in two inter-tropical river basins from the Atlantic Central Africa: the Ogooué and Mbei River basins, Gabon. We analyzed the elem...

The Nature Conservancy, Libreville, Gabon At the global scale and on geological time scales, mechanical erosion and chemical weathering budgets are linked. Together, these processes contribute to the formation and the degradation of the Earth's critical zone and to the biogeochemical cycles of elements. While the weathering of hot and humid shields...

Due to the many factors controlling δ13C values in stalagmites, complicating their paleoclimatic and paleoenvironmental interpretation, most studies do not present δ13C values, but instead focus mainly on δ18O values. This is also the case for most cave studies from tropical South America, where many new δ18O stalagmite records covering the last mi...

In continental volcanic settings, abundant carbonate precipitation can occur with atypical facies compared to marine settings. The (bio-)chemical processes responsible for their development and early diagenesis are typically complex and not fully understood. In the Bolivian Altiplano, Laguna Pastos Grandes hosts a 40-km² carbonate platform with a g...

In continental volcanic settings, abundant carbonate precipitation can occur with atypical facies compared with those of marine settings. The (bio-)chemical processes responsible for their development and early diagenesis are typically complex and not fully understood. In the Bolivian Altiplano, Laguna Pastos Grandes hosts a 40-km2 carbonate platfo...

The geochemistry of riverine sediments exported to the oceans is important for paleo-hydro-climatic reconstruction. However, climate reconstruction requires a good understanding of the relationship between geochemistry and hydrological variability and sediment sources. In this study, we analyzed the major elements, the strontium-neodymium radiogeni...

In the framework of climate changes, peatland ecosystems are compartments of the Critical Zone of growing importance for greenhouse gas (GHG) exchanges with the atmosphere. Peatlands contain about 30 % of the total organic soil carbon worldwide (IPCC, 2019). Interactions of GHG between atmosphere and peatland are potentially controlled by organic m...

The monthly variation of dissolved rare earth elements (REEs) was assessed in the lower Orinoco River during a two year period (2007–2008) to determine the seasonal variability of REE concentrations, to identify the variables that exert the main control in their concentrations and fractionation, and to quantify the annual fluxes of dissolved REEs t...

The present study investigates the processes controlling the elementary and isotopic cycle of the lithium over the Amazon basin. A numerical model is developed to simulate two major processes that have been proposed as key controls of the river lithium isotopic composition: weathering reactions inside the regolith, accounting for secondary phase fo...

We report mineralogical, elemental (major and trace elements) and Sr-Nd isotopic data for suspended particulate matter (SPM) samples from the Amazon, Orinoco and Maroni Rivers collected on a monthly basis over a one-year long hydrological cycle. The aim of this study was i) to characterize the mineralogical and geochemical composition of major Sout...

The chemical weathering budget of land surfaces and the associated CO2 consumption are linked to physical erosion processes at the global scale. The weathering rates of tropical, warm and humid cratonic areas are known to be low due to the shielding effect of deep depleted mature regolith covers (laterites). The silicated cratons which dominate the...

The role of mountains in the geological evolution of the carbon cycle has been intensively debated for the last decades. Mountains are thought to increase the local physical erosion, which in turns promotes silicate weathering, organic carbon transport and burial, and release of sulfuric acid by dissolution of sulfides. In this contribution, we exp...

Most reconstructions of the South American Monsoon System (SAMS) over the last two millennia are based on δ18O records from locations at high-elevation sites in the Andes, which are not influenced by the South Atlantic Convergence Zone (SACZ). Yet the SACZ is a key driver of SAMS variability over much of Brazil. Here we use two new δ18O records fro...

In Ecuador and Peru, geochemical information from Pacific coastal rivers is limited and scarce. Here, we present an unedited database of major element concentrations from five HYBAM observatory stations monitored monthly between 4 and 10 years, and the discrete sampling of 23 Andean rivers distributed along the climate gradient of the Ecuadorian an...

Nas grandes bacias hidrográficas tropicais, os efeitos conjugados da variabilidade climática e das modificaçoes da cobertura do solo são detalhadamente estudados através de várias redes de pesquisa, como o HYBAM (Guyot et al., 2005, Laraque et al., 2005, Filizola, 2003 e Filizola & Guyot, 2004). Porém, as margens dos rios e sua zona hiporreica dest...

A analise geoquimica de sedimentos exportados pelos rios aos oceanos é uma ferramenta importante para a reconstituição paleo-hidro-climatica das bacias hidrológicas continentais mas a interpretação destes resultados necessita calibração de índices geoquímicos em uma escala temporal annual. O objetivo desse estudo e de determinar cual e a resposta d...

Medir a química dos ríos permite de determinar fluxos de material dissolvido producidos por os continentes para os océanos e tambem de identificar as fontes e os factores naturais e anthropogenicos que producem essa matera. Nessa perspectiva o estudio da bacia Amazonica aparece de primeira importancia para a determinaçao dos balances de solutes ao...

The Madeira River is the second largest tributary of the Amazon River. It contributes approximately 13% of the Amazon River flow and it may contribute up to 50% of its sediment discharge to the Atlantic Ocean. Until now, the suspended sediment load of the Madeira River was not well known and was estimated in a broad range from 240 to 715 Mt yr⁻¹. S...

Report of the Franco-Peruvian caving expedition North Peru 2016 (from August 12 to September 20, 2016).

Large hydrological systems aggregate compositionally different waters derived from a variety of pathways. In the case of continental-scale rivers, such aggregation occurs noticeably at confluences between tributaries. Here we explore how such aggregation can affect solute concentration-discharge (C-Q) relationships and thus obscure the message carr...

Although the suspended particulate matter (SPM) of large rivers is mainly provided by the erosion of mountain ranges, the role of Amazon floodplains as short- or long-term sediment storage is still poorly constrained. In this study we use the geochemical and isotope signatures of SPM in the Amazon, the largest world river, coupled with hydrological...

Large hydrological systems such as continental-scale river basins aggregate water from compositionally different tributaries. Here we explore how such aggregation can affect solute concentration-discharge (C-Q) relationships and thus obscure the message carried by these relationships in terms of weathering properties of the Critical Zone. We comput...

At the global scale and on geological time scales, mechanical erosion and chemical weathering budgets are linked. Together, these processes contribute to the formation and the degradation of the Earth’s critical zone and to the biogeochemical cycles of elements. In young orogenic belts, climate and tectonic subsidence control together the rate of t...

Holocene paleoclimatic patterns in NE Brazil are recognized to present singular characteristics when compared with the remaining tropical South-America. In particular, isotopic variations in speleothem calcite highlight that in contrast to the rest of tropical SA, NE Brazil experienced humid conditions during lower summer insolation, i.e. throughou...

Suspended sediment and dissolved load budgets of Peruvian and Ecuadorian Pacific Andean rivers

δ18O en espeleotema es un proxy potente para la reconstrucción de la paleoprecipitación en las zonas tropicales y sub-tropicales. Sin embargo pocos estudios permitieron de presentar variaciones cuantitativas de la lluvia a partir de eses registros. El objetivo de este estudio fue de calibrar la variación de δ18O del carbonato depositado en la cueva...

Reconstrucción de la monzón Sud Americana durante los últimos 10 mil anos y sus efectos en la precipitación del Nordeste de los Andes por medio de registros isotópicos de espeleotemas

Funcionamiento hidrogeoquímico de los sistemas cársticos en la región Alto Mayo

Two well-dated d 18 O-speleothem records from Shatuca cave, situated on the northeastern flank of the Peruvian Andes (1960 m asl) were used to reconstruct high-resolution changes in precipitation during the Holocene in the South American Summer Monsoon region (SASM). The records show that precipitation increased gradually throughout the Holocene in...

Land production potential (LPP) was the maximum grain yield in one year that can be produced by land under the limitations of climate conditions and in the absence of pests and diseases and other factors. Whether climate change was increasing or reducing the LPP in a given region was uncertain. Therefore, Shaanxi Province was selected to analyze th...

The South American Monsoon System (SAMS) is generally considered to be highly sensitive to Northern Hemisphere (NH) temperature variations on multi-centennial timescales. The direct influence of solar forcing on moisture convergence in global monsoon systems on the other hand, while well explored in modeling studies, has hitherto not been documente...

Conference : Climate, sustainability and development, pathways to cooperation under the Science, Technology and Innovation, UIZ-IRD-CGEE

Conference : Rios de los Andes y de la Amazonia, 6ta reunion cientifica del Observatorio HYBAM

Rios de los Andes y de la Amazonia, 6ta reunion cientifica del Observatorio HYBAM

Conference : Rios de los Andes y de la Amazonia, 6ta reunion cientifica del Observatorio HYBAM

The aim of this paper is to evaluate the vulnerability after point source contamination and characterize water circulations in volcanic flows located in the Argnat basin volcanic system (Chaîne des Puys, French Massif Central) using a tracer test performed by injecting a iodide solution. The analysis of breakthrough curves allowed the hydrodispersi...

Silicate weathering budgets of continental basins and identification of the main factors that control them are major issues in geochemistry. In particular, the influence of geomorphological setting on the global weathering budget remains unclear. Dissolved silica (Si) concentration in a river can be used as an index of silicate weathering regime. G...

In this study, eight organic-rich rivers that flow through the Brazilian craton in the southwestern Amazon rainforest are investigated. This investigation is the first of its type in this area and focuses on the effects of lithology, long-term weathering, thick soils, forest cover and hydrological period on the dissolved load compositions in rivers...

A bacia do rio Amazonas é importante no aporte de material dissolvido para o oceano (4% a nível mundial). O objetivo deste trabalho foi estudar a variabilidade espaço-temporal do material inorgânico dissolvido nos principais rios da bacia Amazônica, para o qual foram utilizados dados entre 2003 e 2011 de seis estações hidrológicas do ORE-HYBAM loca...

Formation of mountain ranges results from complex coupling between lithospheric deformation, mechanisms linked to subduction and surface processes: weathering, erosion, and climate. Today, erosion of the eastern Andean cordillera and sub-Andean foothills supplies over 99% of the sediment load passingthrough the Amazon Basin. Denudation rates in the...

Conference : Entendiendo la hidro-geodinamica de la Cuenca Amazónica Peruana

The final publication is available at link.springer.com The dissolved load of the Amazon River is generally considered to be lowly impacted by anthropogenic activities. In this work, based on the chemical and hydrological database of the Environmental Research Observatory—HYBAM (http://www.ore-hybam.org), we explore the importance of the Peruvian F...

From published data based on the HYBAM observatory database, we explore the relationship between silicate weathering rates and physical erosion rates over the Andean basins of the Amazon River.

Conference : International Conference on the Status and Future of the World’s Large Rivers

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Holocene hydroclimate reconstruction from the northeast Peruvian Andes based on high resolution isotope analysis of speleothems from Cascayunga cave.”

The South Atlantic Convergence Zone (SACZ) is considered as the most important feature Monsoon System in South America (SAMS). The central-west region of Brazil is a key region for the reconstruction of the SAMS variability because it is located around axis of the SACZ main activity area. The present results of the stable isotope geochemistry resea...

Présentation in GET Laboratory

Conference : AGU Fall Meeting

Paleoprecipitation Over North-Eastern Peruvian Andes during the Holocene Inferred by Well Dated delta 18O Speleothem Records

Water discharge and suspended and dissolved sediment data from three rivers (Napo, Pastaza and Santiago) in the Ecuadorian Amazon basin and a river in the Pacific basin (Esmeraldas) over a 9-year period, are presented. This data set allows us to present: (a) the chemical weathering rates; (b) the erosion rates, calculated from the suspended sedimen...

5ta reunión científica del ORE HYBAM - Hidroclimatologia y biogeoquimica de las aguas, de los Andes a la Amazonia

5ta reunión científica del ORE HYBAM - Hidroclimatologia y biogeoquimica de las aguas, de los Andes a la Amazonia

5ta reunión científica del ORE HYBAM - Hidroclimatologia y biogeoquimica de las aguas, de los Andes a la Amazonia

5ta reunión científica del ORE HYBAM - Hidroclimatologia y biogeoquimica de las aguas, de los Andes a la Amazonia

5ta reunión científica del ORE HYBAM - Hidroclimatologia y biogeoquimica de las aguas, de los Andes a la Amazonia

5ta reunión científica del ORE HYBAM - Hidroclimatologia y biogeoquimica de las aguas, de los Andes a la Amazonia

This work examined the chemical composition of waters from tributaries of the right bank of the Madeira River which drain silicaterocks of the Brazilian Craton. The study was conducted at the municipalityof Apui, in the southeastern of the Amazonas State, Brazil. There were analyzed pH, conductivity, SiO2 and dissolved ions (Na+, K+, Mg2+ e Ca2+, H...

14to Congresso da Associação Brasileira de Estudos do Quaternário

The suspended sediment yield and associated current denudation rates of eight large catchments located along the eastern range of the central Andes have been determined. The catchments have been chosen as mountainous and mainly denudational basins to avoid sediment sinks that could bias our analysis. Discharge data and suspended sediment concentrat...

Journée scientifique de l’Observatoire HYBAM

The suspended sediment yield and associated current denudation rates of eight large catchments located along the eastern range of the central Andes have been determined. The catchments have been chosen as mountainous and mainly denudational basins to avoid sediment sinks that could bias our analysis. Discharge data and suspended sediment concentrat...

Large river sediments are mostly derived from tectonically active mountain belts, but then undergo a series of sedimentation, temporary storage and reworking episodes on their journey to the ocean. The long transfer time of these sediments through active floodplains might result in a significant chemical maturation via weathering reactions, which i...