Trajectory, fate, and magnitude of continental microplastic loads to the inner shelf: A case study of the world's largest coastal shallow lagoon
The Patos Lagoon estuary is a highly significant ecosystem where freshwater from a vast and densely populated area continuously flows into the Atlantic Ocean by coastal plumes, exporting not only freshwater but also sediment, nutrients, plastics, and other contaminants. In this work, numerical modeling tools together with field data were used to assess for the first time the capacity of the coastal plume to export microplastics (MPs) to the inner shelf under different hydrodynamic conditions. Two field surveys were conducted during plume events to quantify MP concentrations and validate the model approach. A bottom-up approach was employed to estimate the potential MP export from the estuary's domain to the Atlantic Ocean. MP concentration in surface plume waters ranged from 0.20 items m−3 to 1.37 items m−3, confirmed by FTIR as synthetic polymers in a 90 %, being Polypropylene (PP) and Polyethylene (PE) the most abundant in a 73 %. The accumulation pattern was observed on the plume's frontal system, consistent with simulation results. The estimated average MP potential export rate attained 9.0 million items day−1 during moderate plume events and 47.5 million items day−1 during high discharge plume events. Strong discharge events, coupled with intense northeast winds, facilitated rapid southwestward export of MPs. Conversely, moderate to weak discharge events retained MPs closer to the estuary's mouth, enabling either longer trajectories or earlier deposition. Significant MP accumulation hotspots were identified in the gyre between the jetties and Cassino beach, as well as in the saline front within the plume boundaries. These accumulation zones may function as reservoirs for MP particles, potentially posing threats to local ecosystems. Understanding these dynamics is crucial for ongoing monitoring efforts to assess potential harmful interactions over time.
(Science of the Total Environment. vol. 948, n° 0048-9697, pp. 174791, 01/10/2024)
INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Physicochemical behavior and impact of CO2 and CH4 plumes during gas-rich water leakage in a shallow carbonate freshwater aquifer
Carbon capture and storage (CCS) is a promising technology for reducing CO2 emissions. Significant concerns have emerged about the potential leakage of CO2 into shallow aquifers, highlighting the risk to water quality and environmental safety. This underscores the importance of finding monitoring tools suitable for different geological scenarios. If leakage occurs in the context of depleted reservoirs being used for CO2 storage, residual CH4 from the storage complex will likely be entrained together with CO2. However, few studies have addressed the implications of CH4 presence and its potential as a monitoring parameter during CO2 leakage. To address this gap, we simulated a leakage event by injecting water enriched with CO2 and CH4 into a shallow limestone aquifer. The impact of the injection was monitored using a combination of laboratory measurements on water samples and in-situ sensors located downstream from the injection well. All parameters were affected by the simulated leakage. Some monitoring tools allowed us to differentiate the leakage event from natural variations. A key finding of this study was that at 7 m from the injection well, the CH4 breakthrough occurred roughly one day before the CO2 breakthrough, highlighting the potential of CH4 as an early indicator of CO2 leakage and suggesting interesting prospectives for industrial-scale sites. However, further research is needed to confirm the potential of CH4 as a CO2 leakage indicator at industrial scales, due to potential methane oxidation and loss of the signal with longer times and distances. This study contributes to a better understanding of the potential risks and effective monitoring strategies associated with CO2-CH4 leakage in carbonate aquifers.
(Applied Geochemistry. vol. 172, n° 0883-2927, pp. 106122, 01/10/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, IFPEN
Late Miocene transformation of Mediterranean Sea biodiversity
Understanding deep-time marine biodiversity change under the combined effects of climate and connectivity changes is fundamental for predicting the impacts of modern climate change in semi-enclosed seas. We quantify the Late Miocene–Early Pliocene [11.63 to 3.6 million years (Ma)] taxonomic diversity of the Mediterranean Sea for calcareous nannoplankton, dinocysts, foraminifera, ostracods, corals, molluscs, bryozoans, echinoids, fishes, and marine mammals. During this time, marine biota was affected by global climate cooling and the restriction of the Mediterranean’s connection to the Atlantic Ocean that peaked with the Messinian salinity crisis. Although the net change in species richness from the Tortonian to the Zanclean varies by group, species turnover is greater than 30% in all cases, reflecting a high degree of reorganization of the marine ecosystem after the crisis. The results show a clear perturbation already in the pre-evaporitic Messinian (7.25 to 5.97 Ma), with patterns differing among groups and subbasins.
(Science Advances. vol. 10, n° 2375-2548, 27/09/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Influence of estuarine physical processes in the transport of microplastics: a modelling study in the Gironde estuary
(23/09/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, SIAME, UPPA, MIO, IRD, AMU, INSU - CNRS, UTLN, CNRS
Estimating CaCO3 Content Based on Natural Gamma Ray (NGR) in Deep-Ocean Sediment Cores
We present a simple, quick, and high-resolution (approx.10 cm) method for calculating almost continuous calciumcarbonate (CaCO3) proxy records in deep-marine sediment cores based on the well-known dependence of NGR (natural gamma ray) on sediment clay content. The method used in this study is based on the assumption that sediment composition along the SAT (South Atlantic Transect) consists of two components: carbonate and clay. This assumption is reasonably accurate for the region under investigation. At carbonate-rich Site U1583 (66–97 wt% CaCO3), calculated CaCO3 wt% contents are within 4.18% at 1 standard deviation (r) of geochemical analyses of the CaCO3 wt% contents of discrete samples (measured using a coulometer), while at the more lithologically variable Site U1557 (0.1–92 wt% CaCO3), they are within 15.6% at 1r. Results indicate good to excellent correlations between the NGR- and coulometry-derived datasets, supporting the use of this method for carbonate stratigraphy, paleoceanography, and paleoclimate reconstructions. We provide an equation to derive CaCO3 wt% from NGR based on the SAT datasets. The procedure described below can be used to construct the higher resolution proxy CaCO3 records at other sites worldwide compared to discrete CaCO3 values. This method can assist with shipboard lithology determination and can guide core sampling.
(Stratigraphy. vol. 21, pp. 225-242, 20/09/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Ecodynamique des Terres Rares dans les écosystèmes aquatiques : approches pluridisciplinaire et multi-échelle
Les écosystèmes aquatiques sont soumis à de nombreux contaminants, y compris les Terres Rares (REEs), qui forment un groupe cohérent d'éléments aux propriétés physico-chimiques similaires. Au cours des deux dernières décennies, la production et la consommation accrues des REEs pour les technologies modernes ont conduit à leur présence croissante dans les milieux aquatiques. Cependant, des lacunes significatives subsistent qui nécessitent des approches pluridisciplinaires combinant Géochimie et Ecotoxicologie afin de : i) évaluer les cycles géochimiques (distribution, réactivité et devenir) des REEs dans les écosystèmes aquatiques ; et ii) identifier les facteurs et processus contrôlant leurs concentrations dans les organismes aquatiques (biodisponibilité, bioaccumulation). La première partie de ce travail s'est concentrée sur la distribution spatiale et le comportement géochimique des REEs à l'interface continent-océan, principalement en milieu estuarien. L’analyse des concentrations en REEs dissoutes le long d’un profil estuarien dans l’estuaire de la Gironde par condition d’étiage a permis de caractériser le comportement géochimique dans le gradient de salinité avec : (i) un abattement des REEs à faible salinité (S<5), plus importante pour les REEs légères (La, Ce, Pr, Nd) ; (ii) une augmentation des concentrations dissoutes aux salinités intermédiaires (5 (10/09/2024) EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
The effects of a neonicotinoid insecticide, imidacloprid, on the embryo-larval stages of the sterlet sturgeon, Acipenser ruthenus
(03/09/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UR EABX, INRAE
The contribution of near surface geophysics to measure soil related terroir factors in viticulture: A review
Wine quality is affected by environmental factors in the location where the vines are cultivated, in particular the soil and the climate. Major soil-related factors influencing vine development, yield, and berry composition (and thus wine quality) include soil water availability, soil temperature, and soil nutrients, particularly nitrogen. These can be impacted by soil depth and soil compaction. Mapping these factors with classical field-based methods is constraining and expensive. Near surface geophysics (NSG) can be useful in increasing the resolution of data acquisition and, possibly, its cost. Among these techniques, many are already commercially available, but some of them, including Magnetic Resonance Sounding, Induced Polarization and Spectral Analysis of Surface Waves, require a high degree of expertise for acquisition and processing. These should be further developed in order to enlarge the application possibilities. This article reviews soil-related parameters relevant to terroir expression in vineyards and how these can be measured with NSG techniques.
(Geoderma. vol. 449, n° 0016-7061, pp. 116983, 01/09/2024)
UMR EGFV, UB, Bordeaux Sciences Agro, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Role of manganese oxides and oxyhydroxides in phosphate sequestration in natural aquatic environments
Excessive inputs of phosphorus (P) to aquatic environments can lead to eutrophication. Adsorption of phosphate on Fe oxides is one of the main process that can limit P availability. Oxidized forms of Mn have also been suggested to play a role in P trapping. However, although a considerable number of studies have shown the relationships between the geochemistry of Fe and that of phosphates, few studies have attempted to show the direct links between Mn and P. In the present study, we studied the adsorption of phosphate on synthetized Mn(III) and Mn(IV) oxides placed under natural conditions. The aim was to compare the role of Fe and Mn oxides in phosphate adsorption. Two muddy sediments were collected in a river bed at the edge of a large agricultural area. A sandy sediment was collected downstream. A muddy and a sandy sample were taken in a coastal environment. The experiments on phosphate adsorption by sediment and Mn oxides were carried out in slurries containing in situ waters spiked with 10 μM phosphate. Control experiments without Mn-oxide addition showed that the natural sediments tested still had the capacity to adsorb phosphate, in particular due to the presence of reactive Fe(III) oxides, extractable by an ascorbate solution. The addition of Mn(III) and Mn(IV) oxides in much larger quantities than the initial quantity of Fe oxides had little impact on the rate of phosphate adsorption. For both Mn(III) and Mn(IV) oxides, the Mn/P ratio between added particulate Mn and adsorbed P was very high, with values between 260 and 1000. The Fe/P ratio of the iron oxides contained in the slurries was between 6 and 20. On average, the P adsorption capacity of the Fe oxides was 50 times greater than that of the Mn oxides. Manganese oxides are generally less abundant than iron oxides in natural environments. Mn oxides therefore play a minor role in P sequestration compared with Fe oxides. Even if there are environments where Mn oxides can concentrate, the reduction of Mn oxides and subsequent liberation of adsorbed P does not represent a major risk for eutrophication of aquatic ecosystems.
(Chemical Geology. vol. 662, n° 0009-2541, pp. 122231, 01/09/2024)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Subantarctic jet migrations regulate vertical mixing in the Southern Indian
In the Indian sector of the Southern Ocean, the main Antarctic Circumpolar Current (ACC) transport is associated with the subantarctic jet and deviates around several subantarctic islands and volcanic plateaus. This forms regional eddies that are hotspots for productivity, nutrient and CO2 cycling. Though ACC jet migrations related to past climate variations have been reported in previous studies, little is known about their effect on vertical mixing where fronts interact with bathymetry. Here, we investigate past frontal shifts and their impacts on water column structure in the Del Ca˜no Rise, Crozet Archipelago, and Conrad Rise regions over the last 160,000 years by reconstructing surface and subsurface temperatures from siliceous microfossils assemblages in four sediment cores. Our results suggest that the ACC core was displaced equatorward during the last glacial period (70–18 kyrs), away from bathymetric features of the Indian sector of the Southern Ocean. This equatorward shift probably reduced front/bathymetry interactions and, with it, mixing of the upper layer of the ocean in the lee of subantarctic islands and plateaus. We propose that this process participated in the regional isolation of Antarctic Surface Water from deeper water masses. During Marine Isotope Stage (MIS) 5e (132–118 kyrs), an interglacial episode with a warmer-than-modern climate, the reverse situation is reconstructed, whereby the tightening of the ACC fronts against volcanic plateaus probably resulted in enhanced vertical mixing.
(Earth and Planetary Science Letters. vol. 642, n° 0012-821X, pp. 118877, 01/09/2024)
LEMAR, IRD, IFREMER, UBO EPE, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, EPHE, PSL, GSJ, AIST, SFU.ca