Precession and obliquity forcing of the South African monsoon revealed by sub-tropical fires
While the influence of precession on monsoon at low latitudes through insolation forcing is well-known, the role of obliquity is still debated since its influence on the distribution of incoming solar radiation is small in these regions. In southern Africa, long marine and terrestrial sedimentary records attest of a precessional influence on the South African monsoon at orbital time scale. The obliquity signal is occasionally observed in the geological records although modeling results suggest an influence of precession and obliquity on summer monsoon. Here, we present a record of microscopic charcoal from core MD96-2098 located off Namibia covering the past 184,000 years. Our record of fire activity reveals cyclic changes at frequencies of 23, 58 and 12 kyr À1 and lacks the obliquity signal at 41 kyr À1. Changes in fire over southern Africa are interpreted as shifts in large and intense fires spreading in open-grassland savanna as a result of orbitally-driven changes in rainfall intensity associated with the South African monsoon. We show that, despite the absence of a 41 kyr obliquity imprint, the presence of 23, 58 and 12 kyr À1 frequencies likely stems from a nonlinear response of fire to precipitation controlled by a combination of precession and obliquity frequencies, supporting the influence of obliquity on the South African monsoon.
(Quaternary Science Reviews. vol. 310, n° 0277-3791, pp. 108128, 01/06/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UCL, AWI, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, PALEOCEAN, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, CLIM, LSCE, UVSQ, INSU - CNRS, CNRS, DRF (CEA), CEA, IRAP, UT3, Comue de Toulouse, INSU - CNRS, CNRS
Stellar associations powering H ii regions – I. Defining an evolutionary sequence
Connecting the gas in H II regions to the underlying source of the ionizing radiation can help us constrain the physical processes of stellar feedback and how H II re gions evolv e o v er time. With PHANGS-MUSE, we detect nearly 24 000 H II regions across 19 galaxies and measure the physical properties of the ionized gas (e.g. metallicity, ionization parameter, and density). We use catalogues of multiscale stellar associations from PHANGS-HST to obtain constraints on the age of the ionizing sources. We construct a matched catalogue of 4177 H II regions that are clearly linked to a single ionizing association. A weak anticorrelation is observed between the association ages and the H α equi v alent width EW (H α), the H α/ FUV flux ratio, and the ionization parameter, log q . As all three are expected to decrease as the stellar population ages, this could indicate that we observe an evolutionary sequence. This interpretation is further supported by correlations between all three properties. Interpreting these as evolutionary tracers, we find younger nebulae to be more attenuated by dust and closer to giant molecular clouds, in line with recent models of feedback-regulated star formation. We also observe strong correlations with the local metallicity variations and all three proposed age tracers, suggestive of star formation preferentially occurring in locations of locally enhanced metallicity. Overall, EW (H α) and log q show the most consistent trends and appear to be most reliable tracers for the age of an H II region.
(Monthly Notices of the Royal Astronomical Society. vol. 522, n° 0035-8711, pp. 2369 - 2383, 01/06/2023)
MPIA, ANU, UC, RIDI - UPR 9022, IBMC, UNISTRA, CNRS, UNISTRA, INSERM, CNRS, AlfA, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UniCA, LAGRANGE, UNS, INSU - CNRS, UniCA, CNRS, UniCA, UW, CRAL, ENS de Lyon, UCBL, INSU - CNRS, CNRS, ESO, CALTECH, OSU, IPCF, CNR, JHU
Melody of fires in southern Africa over the past 190,000 years
Melody of fires in southern Africa over the past 190,000 years composed by using microcharcoal concentration quantified in the deep-sea sedimentary record MD96-2098 collected off Namibia published in Daniau A.-L., Loutre M.-F., Swingedouw D., Laepple T., Bassinot F., Malaizé B., Kageyama M., Charlier K., Carfantan H. (2023) Precession and obliquity forcing of the South African monsoon revealed by sub-tropical fires. Quaternary Science Reviews, 310, 108128, ISSN 0277-3791, https://doi.org/10.1016/j.quascirev.2023.108128. Piano represents the record of raw data of microcharcoal concentration over the past 190,000 years. Church organ represents the 23,000 years cyclicity in the microcharcoal concentration record. Violin represents the 58,000 years cyclicity in the microcharcoal concentration record.
(25/05/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Production of carbon-containing pyrite spherules induced by hyperthermophilic Thermococcales: a biosignature?
Thermococcales, a major order of hyperthermophilic archaea inhabiting iron- and sulfur-rich anaerobic parts of hydrothermal deep-sea vents, are known to induce the formation of iron phosphates, greigite (Fe 3 S 4 ) and abundant quantities of pyrite (FeS 2 ), including pyrite spherules. In the present study, we report the characterization of the sulfide and phosphate minerals produced in the presence of Thermococcales using X-ray diffraction, synchrotron-based X ray absorption spectroscopy and scanning and transmission electron microscopies. Mixed valence Fe(II)-Fe(III) phosphates are interpreted as resulting from the activity of Thermococcales controlling phosphorus–iron–sulfur dynamics. The pyrite spherules (absent in abiotic control) consist of an assemblage of ultra-small nanocrystals of a few ten nanometers in size, showing coherently diffracting domain sizes of few nanometers. The production of these spherules occurs via a sulfur redox swing from S 0 to S –2 and then to S –1 , involving a comproportionation of (-II) and (0) oxidation states of sulfur, as supported by S-XANES data. Importantly, these pyrite spherules sequester biogenic organic compounds in small but detectable quantities, possibly making them good biosignatures to be searched for in extreme environments.
(Frontiers in Microbiology. vol. 14, n° 1664-302X, 25/05/2023)
IMPMC_ROCKS, IMPMC, MNHN, SU, CNRS, IMPMC_MINENV, IMPMC, MNHN, SU, CNRS, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, I2BC, CEA, CNRS, IMPMC_BIOMIN, IMPMC, MNHN, SU, CNRS, IUF, M.E.N.E.S.R.
On the Role of Gas Compressibility on Foam Injection in Porous Media
Foam injections in porous medium were performed throughout various objectives from Enhanced Oil Recovery (EOR) in 1970s to In Situ Environmental Remediation (ISER) in the mid-1980s. Several foam models were developed with the will to reproduce laboratory experiments and then, field applications related to different working conditions. Nevertheless, compressible effects on the gas phase remain sparsely investigated on both experimentation interpretations and foam models. In this paper, we present a compressible interpretation of a 1D core foam injection experiment, showing that gas compressibility has a pronounced effect despite a relative high working pressure. Based on experimental pressure values along the core, a semi-analytical Local Equilibrium (LE) foam model using a Mobility Factor FM was set and variables behaviour along the core were investigated. Then, foam parameters (fmmob, fmdry and epdry) were determined, and the laboratory experiment was successfully simulated using this compressible solver. Numerical simulations were then performed using the incompressible and compressible solvers. ∇P=f(fg)|Ut=constant\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\nabla P = f(f_g) \vert _{U_t = constant}$$\end{document} extrapolated curves for both solvers were plotted and compared to highlight the role of compressibility. Moreover, coupled effects of foam compressibility and foam rheology were discussed.
(Transport in Porous Media. vol. 148, n° 0169-3913, pp. 459-477, 24/05/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, Bordeaux INP, UBM
Pesticide Residues in French Soils: Occurrence, Risks, and Persistence
Contamination of the environment by pesticide residues is a growing concern given their widespread presence in the environment and their effects on ecosystems. Only a few studies have addressed the occurrence of pesticides in soils, and their results highlighted the need for further research on the persistence and risks induced by those substances. We monitored 111 pesticide residues (48 fungicides, 36 herbicides, 25 insecticides and/or acaricides, and two safeners) in 47 soils sampled across France under various land uses (arable lands, vineyards, orchards, forests, grasslands, and brownfields). Pesticides were found in 98% of the sites (46 of the 47 sampled), including untreated areas such as organic fields, forests, grasslands, and brownfields, with up to 33 different substances detected in one sample, mostly fungicides and herbicides. The concentrations of herbicides were the highest in soils with glyphosate, and its transformation product, AMPA, contributed 70% of the cumulative herbicides. Risk assessment underlined a moderate to high risk for earthworms in arable soils mostly attributed to insecticides and/or acaricides. Finally, the comparison with pesticide application by farmers underlines the presence of some residues long after their supposed 90% degradation and at concentrations higher than predicted environmental concentrations, leading to questions their real persistence in soils.
(Environmental Science and Technology. vol. 57, n° 0013-936X, pp. 7818-7827, 23/05/2023)
Info&Sols, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR ISPA, Bordeaux Sciences Agro, INRAE, LAS, INRAE
On the global synchronicity of glacial vegetation changes
Vegetation responds to local climate and carbon dioxide changes with response times ranging from decades to millennia, depending on location, spatial scale, and vegetation characteristic. Here, we focus on orbital timescales, for which all available estimates suggest an equilibrium of vegetation and climate. Over the course of the last glacial period, global mean temperature varied between minima during Marine Isotope Stage (MIS) 4 and MIS2, and a maximum in MIS3. If orbital-scale climate changes followed this global trend across most of the globe, we would expect vegetation changes to feature a similar temporal evolution.Leveraging a global compilation of pollen records, we quantify the synchronicity of orbital-scale vegetation changes within and across regions during the last glacial period. We use the arboreal pollen fraction, statistical mode decompositions, and key taxa as indicators for forest cover changes. Our results suggest that a globally coherent forest cover minimum occurred during MIS2. However, we do not find evidence for other periods of coherent forest cover trends across the globe or either hemisphere. This indicates that vegetation changes were more regionally confined during earlier parts of the last glacial. As chronologies become more uncertain further back in time, we examine the likelihood of dating errors to explain the absence of globally coherent vegetation changes during MIS4 and MIS3. Finally, we compare our results with simulations of climate and vegetation to assess if models capture the diagnosed forest cover trends found in the pollen records. Moreover, this comparison allows us to infer the influence of temperature, moisture availability, and carbon dioxide on vegetation variations during the last glacial period.
(15/05/2023)
EPHE, PSL, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, UMR ISEM, Cirad, EPHE, PSL, CNRS, UM, IUP
Sampling microplastics in estuarine environments: lessons learned from suspended sediment dynamics and perspectives.
Standardized sampling methods and protocols are essential to facilitate the comparison of studies on plastic pollution and to advance knowledge of this environmental issue. Several protocols for sampling microplastics in oceanic and coastal waters have been developed, compared and even harmonized for this purpose. However, these protocols may be not adapted for the study of estuarine environments, characterized by strong vertical, horizontal and temporal gradients. In this work, microplastic sampling methods and strategies are discussed in relation to estuarine hydrodynamic processes. The analogies between the dynamical behaviour of microplastics and sediments make it possible to draw out recommendations for sampling microplastics based on several decades of research in estuarine hydro-sedimentary dynamics. In particular, we will discuss when, where, and how to sample microplastics in order to capture the most representative picture of microplastic pollution in these highly dynamic systems subject to strong anthropogenic pressures.
(15/05/2023)
EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS
Volcanism and tectonics unveiled in the Comoros Archipelago between Africa and Madagascar
Geophysical and geological data acquired during the 2020–2021 SISMAORE oceanographic cruise reveal a corridor of recent volcanic and tectonic features 200 km wide and 600 km long within and north of Comoros Archipelago in the North Mozambique Channel. More than 2200 submarine volcanic edifices, comparable to the Fani Maoré volcano, have been identified. Most of them are distributed according to two large submarine tectonic-volcanic fields: the N’Drounde province oriented N160°E north of Grande-Comore Island, and the Mwezi province oriented N130°E north of Anjouan and Mayotte Islands. The presence of popping basaltic rocks sampled in the Mwezi suggests post-Pleistocene volcanic activity. The geometry and distribution of recent structures observed on the seafloor are consistent with a current regional dextral transtensional context. Their orientations change progressively from west to east (∼N160°E, ∼N130°E, ∼EW). In the western part, the volcanism could be influenced by the pre-existing structural fabric of the Mesozoic crust. The wide tectono-volcanic corridor underlines the incipient Somalia–Lwandle dextral lithospheric plate boundary between the East-African Rift System and Madagascar. For details see Thinon et al. (2022; doi 10.5802/crgeos.159).
(15/05/2023)
BRGM, iSTeP, INSU - CNRS, SU, CNRS, LMV, IRD, INSU - CNRS, CNRS, UCA, IPGP - UMR_7154, INSU - CNRS, IGN, UR, IPG Paris, CNRS, UPCité, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LGSR, UR, IPG Paris, FST, UR, ITES, ENGEES, UNISTRA, INSU - CNRS, CNRS
First glance of French soil contamination by pesticide residues and the interest for broad-scale monitoring
The intensive use of pesticides in modern agriculture raised concerns about their environmental fate and impacts on the ecosystems. If the monitoring of those substances in water bodies has been established in Europe since the 2000’s, knowledge of soil contamination by such residues is scarce. However, the few studies addressing this issue pointed out the widespread occurrence of pesticides in soils and the risk they can pose for soil biodiversity. This study investigated 111 currently used pesticides in 47 soils sampled across France, mostly from arable lands but also from forest and grasslands theoretically exempted of pesticides applications. The sampling strategy was based on the French Soil Quality Monitoring Network (Jolivet et al., 2022) to evaluate the feasibility of using an existing network for pesticides monitoring in soils. The results demonstrated the widespread contamination of almost all soils samples by residues, including untreated areas such as forests and permanent grasslands. Up to 33 different substances in one soil sample were detected, at concentrations leading to a medium to high ecotoxicological risk for earthworms in arable lands. Several frequently detected residues have never been reported in the literature so far or were found at much lower detection rates. Finally, the comparison with pesticide application records provided by the farmers revealed the unexpected presence of some substance in sites where they were not applied and a longer than expected persistence of several compounds. These findings question the fate of currently used pesticides in the environment under current agricultural practices and advocate for the monitoring of pesticides in soils at broad scales. Filling the knowledge gap of pesticide presence in soil is necessary to understand the contamination of other environmental compartments and prevent their contamination.
(15/05/2023)
Info&Sols, INRAE, EPOC, EPHE, PSL, UB, INSU - CNRS, CNRS, LAS, INRAE