12 results on '"Guinoiseau, D."'
Search Results
2. Characterization of Saharan and Sahelian dust sources based on geochemical and radiogenic isotope signatures
- Author
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Guinoiseau, D., Singh, S. P., Galer, S. J. G., Abouchami, W., Bhattacharyya, R., Kandler, K., Bristow, C., Andreae, M. O., Guinoiseau, D., Singh, S. P., Galer, S. J. G., Abouchami, W., Bhattacharyya, R., Kandler, K., Bristow, C., and Andreae, M. O.
- Abstract
Mineral dust can significantly impact climate and biogeochemical cycles on Earth. To understand dust provenance, an accurate characterization of dust sources and emission regions is required. In this study, we combine rare-earth element patterns, elemental ratios, and radiogenic Sr-Nd-Pb isotopes to discriminate dust sources from key regions in North Africa responsible for similar to 55% of the total dust load emitted annually on Earth. This new dataset, based on fifty-nine analyses of deflatable fine soil material, improves our current knowledge about North African dust sources, especially those underrepresented in Saharan-Sahelian regions. Six potential source areas (PSA) - Libya-Algeria-Mali (PSA(LAM)), Libya-Egypt (PSA(LE)), Bodele Depression (PSA(BD)), Mali Center (PSA(MC)), West African Coast (PSA(WAC)) and Mauritania (PSA(Ma)) - are defined based on several lithogenic tracers as well as on the geological subdivision of North African geological provinces, providing a unique chemical and isotope fingerprint for each PSA. For example, the PSA(BD) - the main dust activation area in North Africa - is clearly distinguished from western African sources using Pb isotopes. Major elements show a large variability within each PSA and are not alone diagnostically useful. Comparison of the newly defined PSA with aerosols collected in remote locations over the North Atlantic shows that their sources are predominantly from western African regions (PSA(LAM) and PSA(WAC)). Bodele-derived dust has a limited impact on the bulk dust transported over the tropical North Atlantic, regardless of the season and altitude of dust transport. The low impact of the Bodele Depression can be explained by a high deposition rate (wet and dry) of aerosols along its southwestward trajectory. A detailed analysis of dust collected over South America during winter will be essential to confirm this observation at a global scale. The present dataset can be efficiently used to track modern dust emiss
- Published
- 2022
3. A multi-isotope and modelling approach for constraining hydro-connectivity in the East African Rift System, southern Ethiopia
- Author
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Markowska, M., Martin, A. N., Vonhof, H. B., Guinoiseau, D., Fischer, M. L., Zinaye, B., Galer, S. J. G., Asrat, A., Junginger, A., Markowska, M., Martin, A. N., Vonhof, H. B., Guinoiseau, D., Fischer, M. L., Zinaye, B., Galer, S. J. G., Asrat, A., and Junginger, A.
- Abstract
During the last African Humid Period (AHP; 15-5 ka), many lakes in the East African Rift System (EARS) experienced pronounced lake-level variations that dramatically transformed the hydrological landscape. Currently dry, saline or marshy-wetland terminal lakes became vast waterbodies, interconnected via overflow sills resulting in the formation of a several thousand-kilometre-long chain of lakes in the EARS. A quantitative, process-based understanding of these hydrological systems can advance our interpretation of past hydroclimate variability from proxy records. Here, we provide a critical modern hydrological dataset for the data-sparse Lake Chew Bahir basin in southern Ethiopia. Driven by modern data, an isotope-enabled hydro-balance model was developed to assess how increases in rainfall modulate delta O-18 and Sr-87/Sr-86 variability. Considering a terminal Lake Chew Bahir scenario, humid conditions resulted in higher lake delta O-18 (similar to+14 parts per thousand) due to increased evaporation and longer water residence times. At the same time Sr-87/Sr-86 Sr decreased from 0.7064 to 0.7061 due to an increased riverine Sr flux characterised by lower, unradiogenic Sr-87/Sr-86 ratios. In a modelling scenario where Lake Chew Bahir became a flow-through system with interconnectivity between lakes Abaya, Chamo, Chew Bahir and Turkana, higher lake delta O-18 (similar to+12 parts per thousand) relative to present was found, but 8 18 0 was lower than in the terminal lake scenario. The lake water Sr-87/Sr-86 ratios (<0.7061) were also slightly lower. A moderate concomitant change in rainfall input delta O-18 of similar to 1 parts per thousand in step with hydrological reorganisation resulted in the lowest lake delta O-18 (similar to+5 parts per thousand). Modelled delta O-18 values were similar to the delta O-18 range of endogenic carbonates from sedimentary cores from Lake Chew Bahir at the onset of the AHP, supporting the validity of our model, and suggesting that ev
- Published
- 2022
4. A multi-isotope and modelling approach for constraining hydro-connectivity in the East African Rift System, southern Ethiopia
- Author
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Markowska, M., primary, Martin, A.N., additional, Vonhof, H.B., additional, Guinoiseau, D., additional, Fischer, M.L., additional, Zinaye, B., additional, Galer, S.J.G., additional, Asrat, A., additional, and Junginger, A., additional
- Published
- 2022
- Full Text
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5. Central Asian modulation of Northern Hemisphere moisture transfer over the Late Cenozoic
- Author
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Prud'homme, C, Scardia, G, Vonhof, H, Guinoiseau, D, Nigmatova, S, Fiebig, J, Gerdes, A, Janssen, R, Fitzsimmons, KE, Prud'homme, C, Scardia, G, Vonhof, H, Guinoiseau, D, Nigmatova, S, Fiebig, J, Gerdes, A, Janssen, R, and Fitzsimmons, KE
- Abstract
Earth’s climatic evolution over the last 5 million years is primarily understood from the perspective of marine mechanisms, however, the role of terrestrial feedbacks remains largely unexplored. Here we reconstruct the last 5 million years of soil moisture variability in Central Asia using paleomagnetism data and isotope geochemistry of an 80 m-thick sedimentary succession at Charyn Canyon, Kazakhstan. We identify a long-term trend of increasing aridification throughout the period, along with shorter-term variability related to the interaction between mid-latitude westerlies and the Siberian high-pressure system. This record highlights the long-term contribution of mid-latitude Eurasian terrestrial systems to the modulation of moisture transfer into the Northern Hemisphere oceans and back onto land via westerly air flow. The response of Earth-surface dynamics to Plio-Pleistocene climatic change in Central Asia likely generated terrestrial feedbacks affecting ocean and atmospheric circulation. This missing terrestrial link elucidates the significance of land-water feedbacks for long-term global climate.
- Published
- 2021
6. Importance of Cadmium Sulfides for Biogeochemical Cycling of Cd and Its Isotopes in Oxygen Deficient Zones—A Case Study of the Angola Basin
- Author
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Guinoiseau, D., Galer, S. J. G., Abouchami, W., Frank, M., Achterberg, E. P., and Haug, G. H.
- Abstract
Understanding oceanic cadmium (Cd) cycling is paramount due to its micronutrient-like behavior in seawater, which has been inferred from its similarity to phosphate (PO4) cycling. Cadmium concentrations follow a nutrient-like consumption-regeneration cycle in the top of the water column and are mainly controlled by water mass mixing and circulation in the deep ocean. However, an additional scavenging mechanism through cadmium sulfide (CdS) precipitates, occurring within sinking biogenic particles in oxygen deficient zones (ODZ), has been proposed. In this study, we report Cd stable isotope and concentration data for seven vertical seawater profiles sampled during GEOTRACES cruise GA08 in the northern Cape and Angola Basins, which feature a significant ODZ along their eastern margins. Outside the ODZ, Cd cycling is similar to that previously reported for the South Atlantic. While water mass mixing largely controls deep ocean Cd isotope signatures, Cd isotope fractionation in surface waters can be modeled as an open system at steady state buffered by organic ligand complexation. In the ODZ, stronger Cd depletion relative to PO4 is associated with a shift in δ114Cd toward heavier values, which is indicative of CdS precipitation. Our interpretation is supported by experimental CdS precipitation data and a size-resolved particle model involving bacterial sulfate reduction as a precursor of CdS. Our estimates of the CdS flux to the seafloor (107 to 109 mol/yr) indicate that CdS precipitation is a significant process of Cd removal and constitutes a nonnegligible Cd sink that needs to be better quantified by Cd isotope analyses of marine sediments.
- Published
- 2019
- Full Text
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7. Importance of Cadmium Sulfides for Biogeochemical Cycling of Cd and Its Isotopes in Oxygen Deficient Zones—A Case Study of the Angola Basin
- Author
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Guinoiseau, D., primary, Galer, S. J. G., additional, Abouchami, W., additional, Frank, M., additional, Achterberg, E. P., additional, and Haug, G. H., additional
- Published
- 2019
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8. Redox control of chromium in the red soils from China evidenced by Cr stable isotopes.
- Author
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Qin X, Guinoiseau D, Ren Z, and Benedetti MF
- Abstract
With chromium isotopes, we study the intricate dynamics of adsorption and redox processes in soil ecosystems, focusing on chromium's behaviour, in red soil profiles enriched with iron-manganese nodules (FMNs) in South China. Key findings reveal that the primary geological source of chromium in the red soil profiles is the weathering of colluvium parent minerals. FMNs have higher chromium concentrations (325-1451 µg/g) compared to surrounding soils (95-247 µg/g) and display stable δ
53 Cr values (0.78 ± 0.17‰), indicating their role as stable chromium repositories, reflecting historical processes. Furthermore, by isolating chromium associated with iron oxides (FeO) and silicate minerals (ReS) within FMNs and surrounding soils using CBD extractions, we show that FeO predominantly carry chromium, particularly in FMNs. The δ53 Cr values of FeO fractions consistently exhibit heavier signatures than ReS fractions, suggesting the sequestration of isotopically heavy chromium (VI) during Fe oxide precipitation. Fluctuations in soil's redox, rather than land use, play a pivotal role in controlling the precipitation of Fe oxides in surrounding soils and the formation of FMNs, thus influencing chromium mobility. This highlights the significance of these factors when utilizing chromium isotopic techniques for source tracking in soil systems, contributing to our understanding of chromium's behaviour in soil environments., Competing Interests: Declaration of Competing Interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests. Benedetti reports financial support was provided by Université Paris Cité- Institut de physique du globe de Paris. Qin reports financial support and travel were provided by China Scholarship Council. Guinoiseau reports financial support was provided by Paris-Saclay University. Ren reports financial support, equipment, drugs, or supplies, and travel were provided by South China Agricultural University. Benedetti reports equipment, drugs, or supplies and travel were provided by National Centre for Scientific Research (CNRS). If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)- Published
- 2024
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9. Cadmium Isotope Fractionation during Complexation with Humic Acid.
- Author
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Ratié G, Chrastný V, Guinoiseau D, Marsac R, Vaňková Z, and Komárek M
- Subjects
- Cadmium analysis, Isotopes, Soil, Humic Substances, Soil Pollutants analysis
- Abstract
Cadmium (Cd) isotopes are known to fractionate during complexation with various environmentally relevant surfaces and ligands. Our results, which were obtained using (i) batch experiments at different Cd concentrations, ionic strengths, and pH values, (ii) modeling, and (iii) infrared and X-ray absorption spectroscopies, highlight the preferential enrichment of light Cd isotopes bound to humic acid (HA), leaving the heavier Cd pool preferentially in solution (Δ
114/110 CdHA-Cd(aq) of -0.15 ± 0.01‰). At high ionic strengths, Cd isotope fractionation mainly depends on its complexation with carboxylic sites. Outer-sphere complexation occurs at equilibrium together with inner-sphere complexation as well as with the change of the first Cd coordination and its hydration complexes in solution. At low ionic strengths, nonspecific Cd binding induced by electrostatic attractions plays a dominant role and promotes Cd isotope fractionation during complexation. This significant outcome elucidates the mechanisms involved in HA-Cd interactions. The results can be used during (i) fingerprinting the available Cd in soil solution after its complexation with solid or soluble natural organic matter and (ii) evaluating the contribution of Cd complexation with organic ligands and phytoplankton-derived debris versus Cd assimilation by phytoplankton in seawater.- Published
- 2021
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10. A frugal implementation of Surface Enhanced Raman Scattering for sensing Zn 2+ in freshwaters - In depth investigation of the analytical performances.
- Author
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Brackx G, Guinoiseau D, Duponchel L, Gélabert A, Reichel V, Zrig S, Meglio JD, Benedetti MF, Gaillardet J, and Charron G
- Abstract
Surface Enhanced Raman Scattering (SERS) has been widely praised for its extreme sensitivity but has not so far been put to use in routine analytical applications, with the accessible scale of measurements a limiting factor. We report here on a frugal implementation of SERS dedicated to the quantitative detection of Zn
2+ in water, Zn being an element that can serve as an indicator of contamination by heavy metals in aquatic bodies. The method consists in randomly aggregating simple silver colloids in the analyte solution in the presence of a complexometric indicator of Zn2+ , recording the SERS spectrum with a portable Raman spectrometer and analysing the data using multivariate calibration models. The frugality of the sensing procedure enables us to acquire a dataset much larger than conventionally done in the field of SERS, which in turn allows for an in-depth statistical analysis of the analytical performances that matter to end-users. In pure water, the proposed sensor is sensitive and accurate in the 160-2230 nM range, with a trueness of 96% and a precision of 4%. Although its limit of detection is one order of magnitude higher than those of golden standard techniques for quantifying metals, its sensitivity range matches Zn levels that are relevant to the health of aquatic bodies. Moreover, its frugality positions it as an interesting alternative to monitor water quality. Critically, the combination of the simple procedure for sample preparation, abundant SERS material and affordable portable instrument paves the way for a realistic deployment to the water site, with each Zn reading three to five times cheaper than through conventional techniques. It could therefore complement current monitoring methods in a bid to solve the pressing needs for large scale water quality data.- Published
- 2020
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11. Are boron isotopes a reliable tracer of anthropogenic inputs to rivers over time?
- Author
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Guinoiseau D, Louvat P, Paris G, Chen JB, Chetelat B, Rocher V, Guérin S, and Gaillardet J
- Subjects
- Paris, Rivers, Boron analysis, Environmental Monitoring methods, Water Pollutants, Chemical analysis, Water Pollution, Chemical statistics & numerical data
- 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 δ11 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 15years 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 δ11 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., (Copyright © 2018 Elsevier B.V. All rights reserved.)- Published
- 2018
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12. Zn Isotope Fractionation during Sorption onto Kaolinite.
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Guinoiseau D, Gélabert A, Moureau J, Louvat P, and Benedetti MF
- Subjects
- Adsorption, Chemical Fractionation, Zinc Isotopes chemistry, Kaolin chemistry, Soil Pollutants chemistry, Zinc chemistry
- Abstract
In this study, we quantify zinc isotope fractionation during its sorption onto kaolinite, by performing experiments under various pH, ionic strength, and total Zn concentrations. A systematic enrichment in heavy Zn isotopes on the surface of kaolinite was measured, with Δ(66)Znadsorbed-solution ranging from 0.11‰ at low pH and low ionic strength to 0.49‰ at high pH and high ionic strength. Both the measured Zn concentration and its isotopic ratio are correctly described using a thermodynamic sorption model that considers two binding sites: external basal surfaces and edge sites. Based on this modeling approach, two distinct Zn isotopic fractionation factors were calculated: Δ(66)Znadsorbed-solution = 0.18 ± 0.06‰ for ion exchange onto basal sites, and Δ(66)Znadsorbed-solution = 0.49 ± 0.06‰ for specific complexation onto edge sites. These two distinct factors indicate that Zn isotope fractionation is dominantly controlled by the chemical composition of the solution (pH, ionic strength).
- Published
- 2016
- Full Text
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