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Valorization of Corn Cobs into Activated Carbon through Chemical Activation and Evaluation of Their Methylene Blue Adsorption Performance for Contaminated Water Treatment
No full textInternational audienceSurface water and groundwater are subject to significant degradation due to human activities. The aim of this study is to evaluate the capacity of methylene blue removal by adsorption on activated carbon derived from corn cobs, activated by H3PO4. The corn cobs were pyrolyzed at 400, 500, and 600 °C; the materials obtained were characterized by FTIR and SEM-EDS to link surface chemistry, elemental composition, and texture. Methylene blue adsorption was evaluated at pH 6.68, followed by UV-Vis spectrophotometry, with adjustment to Langmuir and Freundlich isotherms and thermodynamic analysis between 305.15 and 334.15 K. The results show specific functionalization (P–O–C, P=O groups, –OH, C=O, C=C functions) and hierarchical porosity favorable to kinetics and adsorption capacity. The sample activated at 500 °C exhibits exceptionally high adsorption capacity, with a Qmax of 1,250 mg.g-1, a surface area of 1,887.45 m2.g-1, and a dye removal efficiency of 98.62 %. Separation factors 0 < RL < 1 et between 0.485 and 0.792 indicate favorable adsorption. The thermodynamic study shows ΔH° = +29.20 kJ.mol⁻¹ and ΔS° = +110.643 J.mol⁻¹.K⁻¹, leading to ΔG° < 0, denoting an endothermic, spontaneous process dominated by physisorption reinforced by electrostatic and π–π interactions. In terms of sustainability, this approach valorizes corn cobs as a high-performance adsorbent and provides a local, reliable, and economical solution for treating contaminated water
High temporal variability not trend dominates Mediterranean precipitation
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Emergence of new heat stress hotspots over the West Africa
No full textInternational audienceWe calculate the hourly wet bulb globe temperature (WBGT) values for the last 50 years over Western Africa to assess the emergence of new heatwave hotspots and the interplay between moist and dry heatwaves. In the formulation used, WBGT is derived using the grided data from ERA5 and ERA5-HEAT: 2-m air temperature, relative humidity, 10-m wind speed and mean radiant temperature (a measure of incidence of radiation on a body), and is thus representative of outdoor conditions.We find that the heat stress estimated through WBGT does not peak over the same geographical regions as the air temperature, suggesting an important role of humidity in intensifying heatwaves over certain regions. While the highest temperatures are reached in the northern Sahel and Saharan regions, the highest heat stress values are found further to the south, in the region bordering Senegal, Mauritania and Mali and in southwest Niger. These are the same regions where the WBGT threshold of 33 °C (conditions dangerous even at resting metabolic rates (MR) < 115 W) have recently been crossed for up to 40 hours per year.The duration of exposure to WBGT > 30 °C (conditions dangerous at light physical activity, MR < 180 W) has been increasing over almost the entire West Africa, at rates from 30 to 100 hours/decade. Over the Senegal - Mauritania - Mali border and southern Niger, exposure to WBGT > 33 °C has been increasing by 1-4 hours/decade.Dangerous WBGT thresholds can be crossed at a wide range of temperatures and are often not associated with the highest temperature percentiles. For example, in Niamey, a WBGT of 30 °C has been crossed in the temperature range from ~ 29 to 44 °C, in Thies (Dakar) and Ouagadougou from ~ 28 to 43 °C, and in Abidjan from ~ 28 - 36 °C. In September 2019 and July 2020, in Niamey we find the first occurrences of air temperatures below 36 °C being associated with very dangerous heat stress values (WBGT > 33 ° C).We conclude that for much of continental West Africa, and particularly for the Senegal - Mauritania - Mali border region and southern Niger, extreme heat alerts should at a minimum include indicators accounting for temperature and humidity, in order to capture the dangerous moist heatwave conditions occurring at temperatures well below the highest temperature percentiles. More complex indicators that additionally account for wind and radiation are very desirable for estimates of outdoor safety
High-Resolution Observations Unveil (Sub)Mesoscale Heat Fluxes Shaping Upper-Ocean Heat Content
No full textUpper-ocean heat content (UOHC) regulates air-sea exchange and tropical cyclone intensification; however, its variability at (sub)mesoscale remains insufficiently resolved. Here we combine Surface Water and Ocean Topography (SWOT) observations with high-resolution glider sections in the northeastern tropical Pacific to quantify (sub)mesoscale heat exchange mechanisms. Glider observations reveal large UOHC biases in NOAA-ATBD operational products, arising from climatology errors and unresolved (sub)mesoscale variability. Sharp frontal areas exhibit intense vertical heat exchange driven by ageostrophic circulations, Ekman forcing, and enhanced mixing, with magnitudes comparable to air-sea fluxes. These upward heat pathways rapidly connect thermocline anomalies to the surface layer and modulate the warm-core structure of mesoscale anticyclones, thereby regulating the thermal reservoir available for tropical cyclone intensification. Our results demonstrate that resolving (sub)mesoscale frontal dynamics and associated vertical advection is essential for better constraining UOHC, a key input for cyclone-intensity forecasting
Global occurrences of whistlers detected in the Extremely Low Frequencies during Absolute Scalar Magnetometer burst mode acquisition campaigns of the Swarm mission
No full textInternational audienceThe Absolute Scalar Magnetometer (ASM) of the Swarm satellites acquired data at 250 Hz during monthly one-week campaigns that started in 2019. We process these data to detect and characterise whistler signals in the Extremely Low Frequencies (ELF). Whistler data are now distributed as a Level 2 scientific product of the mission. The corresponding files include whistlers’ characteristics: Their dispersion, their intensity, and the estimated time when these signals entered the ionosphere. This data set contains more than 100,000 whistler events. Global statistics of whistler occurrences between 2019 and 2024 reveal their geographical, local time, seasonal, and solar activity dependencies. Whistlers in ELF occur predominantly during the night at low latitudes, with a depletion close to the magnetic equator. During the rising phase of the solar cycle, an increasing number of whistlers is observed at night, whereas no influence of the solar cycle is observed during the daytime
Annotated checklist of rodents from a biodiversity hotspot, Mount Nimba (West Africa)
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« La fictionnalisation de l’Histoire dans Le Volcan à l’envers de Boris Gamaleya (1983) »
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Etude de l’aérosol atmosphérique par télédétection active. De l’observation locale à l’échelle globale
No full textThis synthesis document largely retraces the evolution of my scientific career, from my doctoral studies at the Service d’Aéronomie (now LATMOS), through my current role as Chair Professor within the European project REALISTIC (CentRe of Excellence in AerosoL remote sensIng technology and Science in The Indian oCean), and including my professorship at the Universitat Politècnica de Catalunya (UPC), where I am currently on leave.Before detailing the scientific aspects of my career, I would like to first highlight a few key figures related to my teaching and research-based training responsibilities:- Teaching at ETSETB (Escola Tècnica Superior d'Enginyeria de Telecomunicació de Barcelona, UPC): 2752 hours taught since 2004 across various subjects from first to fourth year within the five-year engineering program.- Graduate courses in atmospheric remote sensing in the following Master’s programs: MiP, MET, MERIT (UPC), and RNET (Université de La Réunion).- PhD supervision: I have supervised 6 PhD students (2 defended, 4 ongoing). As the French Habilitation à Diriger des Recherches (HDR) does not exist in the Spanish higher education system, I have co-supervised several doctoral theses, and I am currently the sole supervisor (100 %) of two ongoing PhD theses in Spain.- Supervision of 11 Master’s or final-year engineering internships (second and third-year level).I will divide the remainder of this summary into two parts: first, a review of my past scientific trajectory, and second, a presentation of my current research activities at the Université de La Réunion. Since my PhD, my work has focused on the design and development of lidar systems for atmospheric aerosol remote sensing. I began with the construction of a single-wavelength microlidar prototype during my doctoral research and gradually advanced toward more sophisticated lidar systems incorporating cutting-edge receiver channels, such as pure rotational Raman and fluorescence channels. These technological developments have always been coupled withalgorithmic advancements, in which I have also been actively involved. The advanced lidar systems I contributed to develop enable more comprehensive characterization of aerosol optical properties.The resulting multispectral information provides enhanced precision regarding aerosol size, shape, and even composition, which in turn allows for refined classification. Working within collaborative networks such as EARLINET (since 2000) and ACTRIS (since 2011), and coupling ground-based lidar data with satellite observations and transport modeling, I have contributed to the qualitative and quantitative spatiotemporal characterization of aerosols from diverse origins: urban, rural, biomass burning, volcanic eruptions, mineral dust, and even pollen. My 2016 studies on atmospheric pollen using lidar were among the first of their kind in Europe. Since 2012, I have also used radiative transfer models fully parameterized by observations to quantify the direct radiativeeffect of aerosols—particularly mineral dust and, to a lesser extent, biomass burning aerosols. I believe my work on the direct radiative effect of mineral dust across the full shortwave to longwave spectrum has helped raise awareness among climate modelers of the often-overlooked importance of longwave radiative effects. This first major phase of my scientific career was centered on tropospheric aerosols.Since joining LACy on December 1st, 2022, my research has shifted toward studying aerosols in the Indian Ocean region, one of the few remaining relatively “clean” areas on the planet. In this region, local aerosol sources are primarily marine, while long-range transport introduces aerosols from biomass burning and volcanic eruptions. In the tropics, aerosols are vertically distributed within the troposphere (from biomass burning) and the stratosphere (from pyroconvective biomass burning, certain volcanic eruptions, and aerosols of meteoritic or spacecraft re-entry origin). Detecting stratospheric aerosols from the ground requires more powerful lidar systems and remains a technological challenge. I am currently working on the validation and integration of lidar instruments at OPAR (Observatoire de Physique de l’Atmosphère de La Réunion) and of aerosol related variables within the ERIC ACTRIS and NDACC networks. These data—once again combined with satellite observations and modeling—are used to qualitatively and quantitatively characterize the aerosol load over the southwestern Indian Ocean, identify their sources, and understand their climatological cycle and long-term trends. This research, at the core of the REALISTIC project which I lead, aims to improve understanding of the following:- How the “smoke belt” (i.e., the biomass burning regions of southern Africa and South America), in conjunction with the subtropical atmospheric dynamics, contributes to the observed increase in aerosol column content in the southwestern Indian Ocean over the past 15 years.- The chemical composition of aerosols in the stratospheric reservoir, which has remained persistently populated since 2018 and is diversifying (pyroconvective biomass burning, recent powerful volcanic eruptions, and aerosols of extraterrestrial origin).- The regional climate impact of these aerosols, particularly those originating from biomass burning.Given the increasing frequency and severity of wildfires driven by global warming and human activity, a deeper understanding and improved prediction of the climate impacts of the “smoke belt” aerosols —relative to other types of aerosols— at both regional and global scales is now urgently required.Mon document de synthèse retrace en grande partie ma carrière scientifique depuis mes études comme doctorant au Service d’Aéronomie (aujourd’hui LATMOS) à mon poste de professeur sur la chaire de recherche du projet européen REALISTIC (CentRe of Excellence in AerosoL remote rensIng technology and Science in The Indian oCean), en passant bien évidemment par mon poste de professeur à l’Université Polytechnique de Catalogne, poste sur lequel je suis actuellement en «mise à disposition».Avant de passer à l’aspect purement scientifique de ma carrière j’aimerai d’abord rappeler quelques chiffres clés liés à mes tâches d’enseignement et de formateur par la recherche :- Cours à l’ETSETB (Ecole Technique Supérieur en Ingénierie des Télécommunications de Barcelone, Universitat Politècnica de Cataluña) : 2752 heures depuis 2004 dans diverses matières entre la première et la quatrième année du cursus qui est en 5 ans.- Cours en télédétection atmosphérique en masters : MiP, MET, MERIT (Universitat Politècnica de Cataluña) et RNET (Université de la Réunion).- Directeur de thèse de 6 étudiants (2 soutenus, 4 en cours). Dans le système de l’enseignement supérieur espagnol, la HDR n’existe pas. J’ai donc déjà été co-directeur de plusieurs thèses doctorales. Je suis encore actuellement directeur de thèse (100 %) de 2 thèses en Espagne.- Directeur de 11 stages de master ou de 2em ou 3em année d’école d’ingénieur.Je vais scinder la suite de ce résumé en deux. Je présenterai, d’une part, ma trajectoire scientifique passée, puis, d’autre part, ma trajectoire scientifique actuelle à l’Université de la Réunion. Depuis ma thèse j’ai conçu et développé des systèmes lidar pour la télédétection des aérosols atmosphériques depuis un micro lidar à une longueur d’onde (prototype réalisé pendant ma thèse) jusqu’à un lidar avancé avec, e.g., des voies de réception à la pointe de la recherche technologique telles que des voies Raman purement rotationnel ou des voies de fluorescence. Ces développements technologiques sont toujours associés à des développements algorithmiques pour lesquels j’ai été aussi très actif. Ces lidars avancés permettent une caractérisation plus complète des propriétés optiques des aérosols. L’information multispectrale qui en découle permet d’être plus précis sur leur taille, leur forme, voire leur composition, et donc d’affiner leur classification. En travaillant en réseau (EARLINET depuis 2000 ; ACTRIS depuis 2011) et en couplant mesures sol avec des données satellite et de modélisation, essentiellement du transport, j’ai contribué de façon souvent collaborative à une meilleure caractérisation spatio-temporelle, autant qualitative que quantitative, des aérosols d’origine urbaine et rurale, issus de combustion de biomasse, d’éruption volcanique et d’évènement de poussières minérales, ainsi que de pollen. Mes travaux de 2016 sur le pollen atmosphérique mesuré par lidar sont pionniers en Europe. Depuis 2012 j’utilise des modèles de transfert radiatif totalement paramétrisés par de l’observation pour quantifier l’effet radiatif direct de certains aérosols tels que les poussières minérales et en moindre mesure les aérosols issus de combustion de biomasse. Je pense que mes travaux sur l’effet radiatif direct des poussières minérales calculé sur tout le spectre des ondes courtes aux ondes longues a contribué à une prise de conscience des modélisateurs du climat de l’importance des effets radiatifs en ondes longues souvent négligés. Cette première grande étape de mon parcours scientifique est centrée sur les aérosols troposphériques.En arrivant au LACy le 1er décembre 2022 mes intérêts se sont tournés vers l’aérosol présent dans l’Océan Indien, une des rares régions du globe encore relativement « propre ». Ici les sources sont plutôt marines pour l’aérosol local et issues de combustion de biomasse et d’éruption volcanique pour le transport de longue distance. Les aérosols aux tropiques dans notre région se distribuent verticalement dans la troposphère (combustion de biomasse) et dans la stratosphère (combustion de biomasse par pyroconvection, certaines éruptions volcaniques et des aérosols d’origine météoritique ou provenant des débris de ré-entrée de vaisseaux spatiaux/satellites). La détection d’aérosols dans la stratosphère depuis le sol requiert des systèmes lidar plus puissants et représente encore un challenge technologique. Je travaille maintenant à la validation et intégration des instruments lidar de l’OPAR et des variables aérosol générées dans l’ERIC ACTRIS et le réseau NDACC. Ces données, une fois encore couplées à des données satellite et de modélisation, permettent de caractériser qualitativement et quantitativement le contenu en aérosol dans le sud-ouest de l’Océan Indien, de le connecter à ses sources et de déterminer et comprendre son cycle climatologique et sa tendance à long terme. En effet, la motivation de ces travaux, au coeur du projet REALISTIC que je pilote, est de mieux comprendre :- Comment la « smoke belt » (région des feux d’Afrique australe et d’Amérique du sud) combinée à la dynamique atmosphérique subtropicale contribue à l’augmentation observée ces 15 dernières années du contenu en aérosols dans la colonne atmosphérique dans le sud-ouest de l’Océan Indien ;- La composition chimique des aérosols du réservoir stratosphérique qui ne désemplie pas depuis 2018 et se diversifie (combustion de biomasse par pyroconvection, quelques récentes éruptions volcaniques puissantes et des aérosols provenant de l’espace) ;- L’effet sur le climat régional des aérosols mentionnés aux deux points précédents avec un focus particulier sur les aérosols issus de la combustion de biomasse.Compte tenu du dérèglement actuel et futur de l’activité et de la sévérité des feux de forêts liés au réchauffement climatique et l’activité humaine, il est urgent de mieux comprendre et de prévoir les impacts des aérosols émis par la « smoke belt » par rapport au reste des aérosols, globalement et à l’échelle du climat
Un piège de Paul linéaire macroscopique pour étudier l'équilibre de particules microscopiques chargées
No full textWe describe and use a macroscopic linear quadrupolar trap to explore the trapping and equilibrium properties of charged particles. These devices, when operated to trap atomic ions, are at the core of ion based quantum computer and optical atomic clock. To illustrate the characteristics of few particle trapping, and observe different force balance on a charged particle, a macroscopic linear trap, operating at room condition, is trapping micrometer-sized particles. Compared to atomic or molecular ions, their mass can not be neglected and requires an extra voltage for gravity force compensation. We show how this compensation can be demonstrated experimentally and that the choice of hollow-core glass spheres has the advantage of a good reproducibility of the experiments, that allows one to deduce with good precision the charge-to-mass ratio of the trapped particle.</div
