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Jérôme Gaillardet - One of the best experts on this subject based on the ideXlab platform.
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Dynamic of Boron in forest ecosystems traced by its Isotopes: A modeling approach
Chemical Geology, 2020Co-Authors: Benjamin Chetelat, Jérôme Gaillardet, Jiubin ChenAbstract:Understanding the factors that control the cycling of nutrients in terrestrial ecosystems is of fundamental importance given its role for example in nutrient availability to sustain forest productivity, and ultimately in soil carbon storage. In this paper, we developed a model to assess the dynamic of Boron in forest ecosystems and to appraise how the impacts on Boron cycling by internal or external factors should be reflected in the changes of its isotopic compositions across an ecosystem. Despite the scarcity of data, we tested this model on two case studies and were able to reproduce the distribution of Boron Isotopes between the different pools of these two contrasted ecosystems. The model shows a time dependency of the Boron isotopic composition of the different biotic and abiotic compartments of the ecosystem. When the forest grows, a transient enrichment in the heavy isotope up to 20‰ relative to the values at steady-state is observed in the biomass and the soil solutions. The magnitude of this enrichment, and the return time to steady state, are sensitive to B supply and plant demand for Boron. Responses of B dynamic to natural or anthropogenic disturbances is well reflected in the variations of the B isotopic compositions of the different pools that make B Isotopes a good potential tracer of nutrient cycling and by extension make Boron Isotopes a promising proxy for tracing the global functioning of terrestrial biosphere at present and in the past.
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are Boron Isotopes a reliable tracer of anthropogenic inputs to rivers over time
Science of The Total Environment, 2018Co-Authors: Damien Guinoiseau, Pascale Louvat, Guillaume Paris, Jiubin Chen, Benjamin Chetelat, Vincent Rocher, Sabrina Guerin, Jérôme GaillardetAbstract:Abstract This study aims at determining how the Boron signal of the Seine River evolved in terms of concentration and isotopic signatures over eighteen years (1994–95 and 2006–12) and if Boron Isotopes can reliably trace anthropogenic inputs over time. In the anthropised Seine River watershed, Boron is widely released by human activities, and even if Boron concentrations ([B]) are below the potability limit, our study confirms the potential of Boron Isotopes (δ 11 B) to trace urban anthropogenic contaminations. Between 1994 and 2012, [B] have decreased across the anthropised part of the Seine River basin (and by a factor of two in Paris) while δ 11 B has increased. This means either that urban inputs have been reduced or that the Boron signature of urban inputs has changed over time. Both hypotheses are in agreement with the decrease of perborate consumption in Europe over 15 years and are not mutually exclusive. Results of a thorough analysis of urban effluents from the sewage network of Paris conurbation that are in fine released to the Seine River suggest a shift of the urban δ 11 B from −10‰ in 1994 to 1.5 ± 2.0‰ in 2012, in agreement with our second hypothesis. We attribute this change to the removal of perborates from detergents rather than to the modernisation of wastewater treatment network, because it does not significantly impact the wastewater Boron signatures. Eighteen years after the first assessment and despite the decreased use of perborates, geochemical and isotopic mass budgets confirm, that Boron in the Seine River basin is mainly released from urban activities (60–100%), especially in Paris and the downstream part of the basin. Contrastingly, in headwaters and/or tributaries with low urbanisation, the relative Boron input to river from agricultural practices and rains increased, up to 10% and by 10 to 30%, respectively.
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Boron in the Weathering Environment
Boron Isotopes, 2017Co-Authors: Jérôme Gaillardet, Damien LemarchandAbstract:This chapter reviews the state of art of the use of Boron Isotopes to understand water-rock interaction in the Critical Zone, the thin and reactive layer at the Earth’s surface. Because Boron Isotopes are largely fractionated by adsorption, coprecipitation and evaporation-condensation processes, Boron Isotopes are well adapted to trace the main processes that convert rocks into soils and sediments on terrestrial surfaces. The difference in affinity of Boron Isotopes between trigonal and tetrahedral species is the main cause of isotope fractionation of Boron at the Earth’s surface. Due to the competition between the speciation of Boron in solution and the speciation on Boron onto or into solids or gas, large isotopic variations are predicted and observed. Measured Boron isotopic composition in the weathering environment varies over a considerable range of about 70‰. Precipitation, rivers and biomass are usually enriched in 11B, while a complementary depletion in 11B (enrichment in 10B) is observed in clay minerals and on organic or inorganic surfaces. At the ecosystem scale, Boron appears to behave as a micronutrient with a major flux of Boron associated with biological recycling. The inputs of Boron to ecosystems by chemical weathering or from the atmosphere are minor. When the residence time of water in the critical zone is high, such as in groundwater systems, Boron contents increase and are much more dominated by a weathering signal. Boron is mainly added to the ocean by rivers, while the most important sink of Boron is adsorption on clay minerals. This makes Boron a particularly good tracer of the weathering/erosion balance of terrestrial surfaces in addition to its capacity for tracing the pH and ancient seawater. A lot remains to be done to better understand the behavior of Boron and Boron Isotopes at the Earth’s surface and on the secular evolution of Boron Isotopes in the ocean but our review of the available literature shows that this tracer has a great potential at a local (ecosystem) and global (ocean) scale.
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A fully automated direct injection nebulizer (d-DIHEN) for MC-ICP-MS isotope analysis: application to Boron isotope ratio measurements
Journal of Analytical Atomic Spectrometry, 2014Co-Authors: Pascale Louvat, Guillaume Paris, Julien Moureau, Julien Bouchez, Johanna Noireaux, Jérôme GaillardetAbstract:This work presents a fully automated setup for using direct injection nebulization as an introduction system for solution measurements by MC-ICP-MS, here applied to Boron Isotopes in pure boric acid solutions and natural samples. In this setup, a direct injection nebulizer (d-DIHEN) is plugged into the plasma torch without any spray chamber, and an automated 6-port valve interfaces the nebulizer and the autosampler. The advantages of a d-DIHEN for Boron isotope ratio measurements are high sensitivity and short washout times, allowing for sample-standard bracketing (SSB) measurements at a higher rate than spray chambers. The measurement of Boron Isotopes by MC-ICP-MS at an unprecedented sub 0.1 parts per thousand, repeatability level (2 standard deviation = 2SD) was achieved for pure boric acid solutions. The improved precision is allowed by a better stability of the introduction system with continuous operation of the peristaltic pump (which was manually switched off between samples before automation) and due to the possibility of multiple analyses of the same sample solution. However, such a good repeatability was not systematically obtained for Boron Isotopes SSB measurements of natural samples (in fine 2SD are between 0.02 and 0.5 parts per thousand). Boron from natural samples has to be extracted before isotope analysis, with one to four steps depending on the sample type. Repeated analyses of Boron independently separated up to ten times from the same sample lead to an external reproducibility no better than 0.2 parts per thousand. Boron chemical separation from the samples prior to MC-ICP-MS analyses seems to remain the main limitation to precise measurements of Boron isotope ratios.
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Geological evolution of seawater Boron isotopic composition recorded in evaporites
Geology, 2010Co-Authors: Guillaume Paris, Jérôme Gaillardet, Pascale LouvatAbstract:The abundance of Boron Isotopes in ancient marine carbonates can be used to estimate oceanic pH that reflects atmospheric CO 2 levels. This proxy requires that the Boron isotopic composition of seawater at the time the carbonate has formed is known, and thus the past changes in seawater chemistry. Here we report the Boron isotopic composition of selected ancient marine halites and modern sea salts. The signal, interpreted as marine, reveals a clear evolution of the Boron isotopic composition of seawater (to 8‰ variations over the Cenozoic). Comparison between this reconstructed curve and the Mg/Ca ratio reveals a high level of consistency that will help to better define oceanic geochemical cycles.
Christian Ercolani - One of the best experts on this subject based on the ideXlab platform.
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insights on catchment wide weathering regimes from Boron Isotopes in riverine material
Geochimica et Cosmochimica Acta, 2019Co-Authors: Christian Ercolani, Damient Lemarchand, Anthony DossetoAbstract:Abstract Chemical weathering contributes to the regulation of the global carbon cycle and biogeochemical cycles. Accordingly, the identification of the parameters that control weathering reactions and transport of weathering signals at the catchment scale is essential. The use of Boron (B) Isotopes have been shown to be a useful proxy in tracing weathering reactions due to large isotope fractionation during weathering processes. However, our knowledge of how Boron Isotopes record the weathering regime at the catchment scale and how that weathering signal is transported from source areas to the depositional environment remains limited. Here we characterize B isotope and major element behavior during chemical weathering and transport by analyzing the B isotopic (δ11B) and element compositions of riverine material (riverbank sands ( In the Murrumbidgee, two distinct weathering regimes are present, one where mineral dissolution is associated with minimal neoformation at higher elevations and another where mineral neoformation dominates at lower elevations and in granitic lithologies. Significant B isotope difference between the clay fraction and the bedrock (Δ11Bclay-bedrock) is observed in most monolithological catchments at high mean elevation (excluding granites), which correlates with a large B depletion. Smaller isotope difference between the clay fraction and bedrock is observed in monolithological catchments at lower elevations as well as in granitic catchments at all elevations and is associated with limited B removal. These results suggest that lithology and catchment topography influence B mobility during weathering and the isotopic composition of weathering products. By mass balance calculation, the B isotope and chemical composition of the clay and sand fractions in the Murrumbidgee River can be explained as a mixture of the clays and sands produced throughout the catchment delivered to the main channel by the tributaries. These results indicate that there is little or no chemical and isotopic modification of the river sediment during fluvial transport and that weathering signal produced in the sediment source areas is transferred to the depositional environment without significant modification. The Boron content of the clay-sized fraction (∼40 ppm) is several orders of magnitude greater than that of the dissolved load while B isotope compositions of the clay-sized fraction are isotopically much lighter (up to 40‰). Because a maximum isotopic difference of 30‰ between the dissolved and solid phases is expected during adsorption processes, the observed isotope compositions in the dissolved load and the sediment clay fraction cannot be explained by pH-driven B partitioning. These observations suggest that clays are not directly precipitating from solutions compositionally similar to surface waters; deeper soil solutions are expected to play a significant role in clay formation. This research highlights the potential of B Isotopes in river sediments to describe the present and past weathering regimes at the catchment scale, including possible paleoenvironment reconstruction as the B isotope signature of riverine material records the conditions of its formation.
Gary N Hemming - One of the best experts on this subject based on the ideXlab platform.
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Boron Isotopes a paleo ph meter for tracking ancient atmospheric co2
Elements, 2017Co-Authors: Troy E Rasbury, Gary N HemmingAbstract:The Boron isotope composition of calcium carbonate shells of marine organisms has the unique potential to record surface ocean pH, allowing the calculation of atmospheric p CO 2 due to the established relationship between pH and the partial pressure of (atmospheric) CO 2 ( p CO 2 ). This “paleo-pH meter” allows scientists to produce a record of the natural fluctuations of atmospheric p CO 2 over geologic time, which will help us better understand the impacts of the recent anthropogenic addition of CO 2 to Earth9s atmosphere. Towards this end, a tremendous effort to understand the systematics of Boron uptake in marine carbonates is underway. Here, we review the potential of Boron Isotopes to constrain ocean pH and, thus, atmospheric p CO 2 .
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atmospheric carbon dioxide concentration across the mid pleistocene transition
Science, 2009Co-Authors: Bärbel Hönisch, Gary N Hemming, David Archer, Mark E. Siddall, Jerry F McmanusAbstract:The dominant period of Pleistocene glacial cycles changed during the mid-Pleistocene from 40,000 years to 100,000 years, for as yet unknown reasons. Here we present a 2.1-million-year record of sea surface partial pressure of CO2 (Pco2), based on Boron Isotopes in planktic foraminifer shells, which suggests that the atmospheric partial pressure of CO2 (pco2) was relatively stable before the mid-Pleistocene climate transition. Glacial Pco2 was ~31 microatmospheres higher before the transition (more than 1 million years ago), but interglacial Pco2 was similar to that of late Pleistocene interglacial cycles (
Anthony Dosseto - One of the best experts on this subject based on the ideXlab platform.
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insights on catchment wide weathering regimes from Boron Isotopes in riverine material
Geochimica et Cosmochimica Acta, 2019Co-Authors: Christian Ercolani, Damient Lemarchand, Anthony DossetoAbstract:Abstract Chemical weathering contributes to the regulation of the global carbon cycle and biogeochemical cycles. Accordingly, the identification of the parameters that control weathering reactions and transport of weathering signals at the catchment scale is essential. The use of Boron (B) Isotopes have been shown to be a useful proxy in tracing weathering reactions due to large isotope fractionation during weathering processes. However, our knowledge of how Boron Isotopes record the weathering regime at the catchment scale and how that weathering signal is transported from source areas to the depositional environment remains limited. Here we characterize B isotope and major element behavior during chemical weathering and transport by analyzing the B isotopic (δ11B) and element compositions of riverine material (riverbank sands ( In the Murrumbidgee, two distinct weathering regimes are present, one where mineral dissolution is associated with minimal neoformation at higher elevations and another where mineral neoformation dominates at lower elevations and in granitic lithologies. Significant B isotope difference between the clay fraction and the bedrock (Δ11Bclay-bedrock) is observed in most monolithological catchments at high mean elevation (excluding granites), which correlates with a large B depletion. Smaller isotope difference between the clay fraction and bedrock is observed in monolithological catchments at lower elevations as well as in granitic catchments at all elevations and is associated with limited B removal. These results suggest that lithology and catchment topography influence B mobility during weathering and the isotopic composition of weathering products. By mass balance calculation, the B isotope and chemical composition of the clay and sand fractions in the Murrumbidgee River can be explained as a mixture of the clays and sands produced throughout the catchment delivered to the main channel by the tributaries. These results indicate that there is little or no chemical and isotopic modification of the river sediment during fluvial transport and that weathering signal produced in the sediment source areas is transferred to the depositional environment without significant modification. The Boron content of the clay-sized fraction (∼40 ppm) is several orders of magnitude greater than that of the dissolved load while B isotope compositions of the clay-sized fraction are isotopically much lighter (up to 40‰). Because a maximum isotopic difference of 30‰ between the dissolved and solid phases is expected during adsorption processes, the observed isotope compositions in the dissolved load and the sediment clay fraction cannot be explained by pH-driven B partitioning. These observations suggest that clays are not directly precipitating from solutions compositionally similar to surface waters; deeper soil solutions are expected to play a significant role in clay formation. This research highlights the potential of B Isotopes in river sediments to describe the present and past weathering regimes at the catchment scale, including possible paleoenvironment reconstruction as the B isotope signature of riverine material records the conditions of its formation.
Catherine Guerrot - One of the best experts on this subject based on the ideXlab platform.
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Boron Isotope Variation During Flood Events in a Mediterranean Basin: Tracer of the Water Compartments (Hérault, S. France)☆
Procedia Earth and Planetary Science, 2015Co-Authors: Emmanuelle Petelet-giraud, Philippe Négrel, Catherine GuerrotAbstract:Abstract Boron Isotopes were measured during 3 flood events at the outlet of the Herault watershed in complement with Sr Isotopes. The main water sources (i.e. karst aquifer and the tributaries) were also constrained in high and low flows. Boron Isotopes are controlled both by natural and anthropogenic inputs (sewage effluents and/or fertilizers) whereas Sr Isotopes trace the various lithologies in the basin. The signature of the Herault River during flood events presents isotopic variations as large as 15 delta units for Boron Isotopes, revealing the various contributions of the water compartments according to the rainfall intensity, duration and location.
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Combining Boron Isotopes and carbamazepine to monitor artificial recharge (southern Mediterranean)
2014Co-Authors: Lise Cary, Catherine Guerrot, Joël CasanovaAbstract:The groundwater resources of coastal areas are highly vulnerable, being located either in complex hydrogeological structures or in local shallow aquifers where water stress and salt water intrusion occur under the multiple constraints governed by increasing anthropogenic pressures and climatic conditions. Yet, recent integrated water resource planning often relies on alternative water supplies. In order to limit seawater intrusion in an agricultural overexploited watershed and to ensure water availability, managed aquifer recharge with treated wastewater was settled in the Korba aquifer on the east coast of Tunisia. Water quality monitoring was implemented in order to determine the different system components and to trace the effectiveness of the artificial recharge. Groundwater samples taken from recharge control piezometers and surrounding farm wells were analyzed for their chemical contents, for their Boron Isotopes, a proven tracer of groundwater salinization and domestic sewage, and their carbamazepine content, an anti-epileptic known to pass through wastewater treatment and so recognized as a pertinent tracer of wastewater contamination. The aquifer system is constituted by the superficial and shallow Plio-Quaternary formations and by the deeper Miocene units which constitute its basement. Marine Pliocene sediments display interbedded sandstone-sand-marl topped with variably clayey sandstone. Quaternary deposits are mainly made of fossiliferous carbonated sandstones. The system equilibrium was permanently disturbed by the different temporal dynamics of continuous processes such as cation exchange, and by threshold processes linked to oxidation-reductive conditions. The Boron isotopic compositions of groundwaters displayed a significant variability (10 - 45 ‰) and significantly shifted back-and-forth due to mixing with end-members of various origins. Under the variable contribution of meteoric recharge, the Plio-Quaternary groundwater was subject to seawater intrusion that locally induced high δ11B values superior to the seawater signature (δ11B > 39 ‰, no carbamazepine). The managed recharge water (δ11B of 10.7-13.8 ‰) was brackish and of poor quality with a carbamazepine content showing a large short term variability with an average daily level of 328 ± 61 ng/L. A few piezometers in the vicinity of the recharge site gradually acquired a B isotopic composition close to the wastewater signature with increasing carbamazepine contents (from 20 to 910 ng/L). The combination of Boron isotopic signatures with Boron and carbamazepine contents can be a useful tool to assess sources and mixing of treated wastewaters in groundwaters.
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Combining Boron Isotopes and carbamazepine to trace sewage in salinized groundwater: a case study in Cap Bon, Tunisia
Applied Geochemistry, 2013Co-Authors: Lise Cary, Joël Casanova, Noureddine Gaaloul, Catherine GuerrotAbstract:The Korba aquifer on the east coast of Cape Bon has been overexploited since the 1960s with a resultant reversal of the hydraulic gradient and a degradation of the quality due to seawater intrusion. In 2008, the authorities introduced integrated water resources planning based on a managed aquifer recharge with treated wastewater. Water quality monitoring was implemented in order to determine the different system components and trace the effectiveness of the artificial recharge. Groundwater samples taken from recharge control piezometers and surrounding farm wells were analyzed for their chemical contents, for their Boron Isotopes, a proven tracer of groundwater salinization and domestic sewage, and their carbamazepine content, an anti-epileptic known to pass through wastewater treatment and so recognized as a pertinent tracer of wastewater contamination. The system equilibrium was permanently disturbed by the different temporal dynamics of continuous processes such as cation exchange, and by threshold processes linked to oxidation-reductive conditions. The Boron isotopic compositions significantly shifted back-and-forth due to mixing with end-members of various origins. Under the variable contribution of meteoric recharge, the Plio-Quaternary groundwater (δ11B of 35-40.6‰, a mean B concentration of 30 µmol/L, no carbamazepine, n=7) was subject to seawater intrusion that induced a high δ11B level (δ11B of 41.5-48.0‰, a mean B concentration of 36 µmol/L, and n=8). Fresh groundwater (δ11B of 19.89‰, B concentration of 2.8 µmol/L, no carbamazepine) was detected close to the recharge site and may represent the deep Miocene pole which feeds the upper Plio-Quaternary aquifer. The managed recharge water (δ11B of 10.67-13.8‰, n=3) was brackish and of poor quality with a carbamazepine content showing a large short term variability with an average daily levels of 328 ± 61 ng/L. A few piezometers in the vicinity of the recharge site gradually acquired a B isotopic composition close to the wastewater signature and showed an increasing carbamazepine content (from 20 to 910 ng/L). The combination of Boron isotopic signatures with Boron and carbamazepine contents is a useful tool to assess sources and mixing of treated wastewaters in groundwaters. Effluent quality needs to be greatly improved before injection to prevent further degradation of groundwater quality.
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Effect of artificial recharge by treated wastewater on the quality of the Korba coastal aquifer (Cape Bon, Tunisia): insights from Boron Isotopes.
2012Co-Authors: Lise Cary, Catherine Guerrot, Joël Casanova, Noureddine Gaaloul, Amira Mekni, Emmanuelle Petelet-giraudAbstract:Mediterranean coastal aquifers are highly stressed, partly because of intensive agricultural activities in semi-arid or arid context. Water quality of groundwater is often degraded by different processes: salt water intrusion, diffuse pollution... In this context, the Korba aquifer on the eastern coast of Cape Bon (Tunisia) undergoes overexploitation. Since the 60's, reversal of hydraulic gradient and saline intrusion were studied (Ennabli, 1980; Kouzana et al. 2009a , 2009b; Kouzana et al., 2010) and the groundwater hydrogeological functioning was modeled (Kerrou et al., 2010; Panicoti et al. 2001a, 2001b; Zghibi et al., 2011). Crucial for local agriculture, aquifer management led to the implementation of artificial recharge with treated wastewaters at the end of 2008. Since then, groundwater quality was monitored to trace the effectiveness of artificial recharge, based on Boron Isotopes, to better determine the different system components. Samples were taken from recharge control piezometers and in farmers' wells. Cation exchange was demonstrated to be one of the main processes controlling the groundwater quality. Sodium, potassium and Boron were clearly in deficit compared to a mixing line with seawater, whereas calcium, strontium and bicarbonates were in excess. Treated wastewaters were concentrated in chloride and sodium and sometimes more than in wells, equivalent to a mixing of 6 to 14 % with sea water. The 2009 isotopic signatures in wells were clearly distributed on a mixing line between a nitrate-polluted and salinized pole especially constituted by abandoned wells and which had already reached equilibrium governed by cation exchange or sorption processes, and fresh groundwater. This mixing line explained the intermediate composition of a less salinized groundwater pole of intensively pumped wells. In 2010, in a context of low rainwater inputs, a general decrease of 11B in the same wells may indicate mixing with deeper groundwaters and a continuous isotopic re-equilibration between the two previous end-members according to the different inputs, e. g. rainwater recharge or river flows. 11B increased between 2010 and 2011 up to their 2009 value. Such a variation between 2010 and 2011 cannot be linked to a simple cation exchange but appear more reasonably linked to a higher rainfall recharge after a rainy winter. The mixing of treated wastewater was estimated at a maximum of 30 % with groundwaters and seemed very local. According to fluxes directions, artificial recharge could clearly not influence some wells composition. The impact of artificial recharge seemed thus very limited in terms of quality: recharge waters were salted and poorly contribute to refresh the system. Ultimately, the degradation of irrigated soils and crops diversity, currently limited by salt tolerance, will not improve. Moreover, B Isotopes showed that artificial recharge seemed to influence some piezometers at vicinity but had low impact, if any, on close farmers' wells.