Raisonner la densification des espaces urbanisés face aux enjeux des continuités écologiques

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Iodide, iodate & dissolved organic iodine in the temperate coastal ocean

The surface ocean is the main source of iodine to the atmosphere, where it plays a crucial role including in the catalytic removal of tropospheric ozone. The availability of surface oceanic iodine is governed by its biogeochemical cycling, the controls of which are poorly constrained. Here we show a near two-year time series of the primary iodine species, iodide, iodate and dissolved organic iodine (DOI) in inner shelf marine surface waters of the Western English Channel (UK). The median ± standard deviation concentrations between November 2019 and September 2021 (n=76) were: iodide 88 ± 17 nM (range 61-149 nM), iodate 293 ± 28 nM (198-382 nM), DOI 16 ± 16 nM (<0.12-75 nM) and total dissolved iodine (dIT) 399 ± 30 nM (314-477 nM). Though lower than inorganic iodine ion concentrations, DOI was a persistent and non-negligible component of dIT, which is consistent with previous studies in coastal waters. Over the time series, dIT was not conserved and the missing pool of iodine accounted for ~6% of the observed concentration suggesting complex mechanisms governing dIT removal and renewal. The contribution of excess iodine (I*) sourced from the coastal margin towards dIT was generally low (3 ± 29 nM) but exceptional events influenced dIT concentrations by up to ±100 nM. The seasonal variability in iodine speciation was asynchronous with the observed phytoplankton primary productivity. Nevertheless, iodate reduction began as light levels and then biomass increased in spring and iodide attained its peak concentration in mid to late autumn during post-bloom conditions. Dissolved organic iodine was present, but variable, throughout the year. During winter, iodate concentrations increased due to the advection of North Atlantic surface waters. The timing of changes in iodine speciation and the magnitude of I* subsumed by seawater processes supports the paradigm that transformations between iodine species are biologically mediated, though not directly linked

A Global Model for Iodine Speciation in the Upper Ocean

An ocean iodine cycling model is presented, which predicts upper ocean iodine speciation. The model comprises a three-layer advective and diffusive ocean circulation model of the upper ocean and an iodine cycling model embedded within this circulation. The two primary reservoirs of iodine are represented, iodide and iodate. Iodate is reduced to iodide in the mixed layer in association with primary production, linked by an iodine to carbon (I:C) ratio. A satisfactory model fit with observations cannot be obtained with a globally constant I:C ratio, and the best fit is obtained when the I:C ratio is dependent on sea surface temperature, increasing at low temperatures. Comparisons with observed iodide distributions show that the best model fit is obtained when oxidation of iodide back to iodate is associated with mixed layer nitrification. Sensitivity tests, where model parameters and processes are perturbed, reveal that primary productivity, mixed layer depth, oxidation, advection, surface freshwater flux, and the I:C ratio all have a role in determining surface iodide concentrations, and the timescale of iodide in the mixed layer is sufficiently long for nonlocal processes to be important. Comparisons of the modeled iodide surface field with parameterizations by other authors show good agreement in regions where observations exist but significant differences in regions without observations. This raises the question of whether the existing parameterizations are capturing the full range of processes involved in determining surface iodide and shows the urgent need for observations in regions where there are currently none

Marine iodine emissions in a changing world

Iodine is a critical trace element involved in many diverse and important processes in the Earth system. The importance of iodine for human health has been known for over a century, with low iodine in the diet being linked to goitre, cretinism and neonatal death. Research over the last few decades has shown that iodine has significant impacts on tropospheric photochemistry, ultimately impacting climate by reducing the radiative forcing of ozone (O 3) and air quality by reducing extreme O 3 concentrations in polluted regions. Iodine is naturally present in the ocean, predominantly as aqueous iodide and iodate. The rapid reaction of sea-surface iodide with O 3 is believed to be the largest single source of gaseous iodine to the atmosphere. Due to increased anthropogenic O 3, this release of iodine is believed to have increased dramatically over the twentieth century, by as much as a factor of 3. Uncertainties in the marine iodine distribution and global cycle are, however, major constraints in the effective prediction of how the emissions of iodine and its biogeochemical cycle may change in the future or have changed in the past. Here, we present a synthesis of recent results by our team and others which bring a fresh perspective to understanding the global iodine biogeochemical cycle. In particular, we suggest that future climate-induced oceanographic changes could result in a significant change in aqueous iodide concentrations in the surface ocean, with implications for atmospheric air quality and climate

Global sea-surface iodide observations, 1967-2018

The marine iodine cycle has significant impacts on air quality and atmospheric chemistry. Specifically, the reaction of iodide with ozone in the top few micrometres of the surface ocean is an important sink for tropospheric ozone (a pollutant gas) and the dominant source of reactive iodine to the atmosphere. Sea surface iodide parameterisations are now being implemented in air quality models, but these are currently a major source of uncertainty. Relatively little observational data is available to estimate the global surface iodide concentrations, and this data has not hitherto been openly available in a collated, digital form. Here we present all available sea surface (<20 m depth) iodide observations. The dataset includes values digitised from published manuscripts, published and unpublished data supplied directly by the originators, and data obtained from repositories. It contains 1342 data points, and spans latitudes from 70°S to 68°N, representing all major basins. The data may be used to model sea surface iodide concentrations or as a reference for future observations

Translational research in innovative biomarkers in kidney allograft rejection : allowing transfer of clinical research to clinical practice and providing new insights to basic science

Les avancées technologiques ont permis l'avènement de biomarqueurs innovants pour l'évaluation des lésions du greffon rénal. Toutefois, notre raisonnement médical pour décider d'une biopsie repose toujours sur des données biologiques conventionnelles peu performantes. Au cours de ce travail de thèse, nous avons émis l'hypothèse que le préalable au transfert des biomarqueurs de la recherche vers la clinique était la robustesse de la sélection des candidats puis leur intégration dans des modèles multiparamétriques validés montrant un bénéfice clinique net. Certains biomarqueurs étant des acteurs de la réponse immunitaire alloimmune, nous avons postulé que la découverte de signatures moléculaires diagnostiques du rejet pouvait apporter de nouvelles hypothèses physiopathologiques. Dans un premier travail, nous avons optimisé l'utilisation des chimiokines urinaires CXCL9 et CXCL10 pour le diagnostic non-invasif du rejet aigu. L'expression de ces cytokines chimiotactiques est augmentée dans les urines des patients au cours du rejet aigu, mais également lors des infections urinaires (IU) ou de la réplication du BK virus (BKV) pouvant constituer des facteurs de confusion. Nous avons mesuré les protéines CXCL9 et CXCL10 dans 391 échantillons urinaires, prélevés concomitamment d'une biopsie du greffon, d'un examen cytobactériologique des urines et d'une charge virale sanguine du BK virus. Les concentrations urinaires de CXCL9 et CXCL10 étaient augmentées en cas d'IU, de même qu'en cas virémie à BKV, associée ou non à une néphrite virale (P1) in ABMR cases, were regulated by one of the 3 miRNAs. In silico analyses suggested an enrichment in myeloid-derived pathways, and among PBMC subsets, the 3 miRNAs were confirmed to be mainly originating from classical monocytes. This research work identified the confusion factors in using urinary chemokines as non-invasive markers of acute rejection, and as a first we built a multiparametric well-validated model which proved its clinical utility. Moreover, our data provide new insights in miRNAs as biomarkers as well as key-player in ABMR. The link between monocytes response in the blood and their infiltrating properties in the allograft could provide new insights to pathological mechanisms in ABMR

Restitution des propriétés microphysiques et radiatives des nuages froids et mixtes à partir des données du système RALI (RAdar-LIdar)

Membres du jury Mr. Claude Klapisz Mr Jean-Francois Gayet Mr Anthony Illingworth Mr Chung-Chi Lin Mr Jacques Pelon Mr Jacques TestudClouds play an important role in atmospheric processes and climate control. However their parametric representation in numerical models for weather forecast and climate is still simplistic and not yet validated. The desire to understand the radiative impact of clouds has driven the definition of two space missions using a radar-lidar combination (CLOUDSAT/CALIPSO and EarthCARE). The RALI system (synergetic Cloud Radar- Lidar system) is an airborne demonstrator for both of the above-mentioned instruments that help at once the development of the associated algorithms and the calibration of the space mission products. Thus, RALI aims at the development and exploitation of a synergetic airborne or ground-based radar-lidar combination in order to document vertical profiles of microphysical, dynamical and radiative properties of non-precipitating iced clouds. This thesis comes within this scope. At first, an inverse model relating remote sensing variables to the cloud parameters was built. This model enables to free from the shape of the particle size distribution and is used as the basic principle of the radar-lidar synergetic algorithm. This algorithm was also developed to take into account the natural vertical variability of cloud particles concentration. Simulation tests were performed in order to determine robustness, precision and the optimal conditions of application. Results from field experiment (CLARE 98, CARL 99, CLARE 2000) were compared with in-situ microphysical measurements and have demonstrated the capacity of the algorithm to retrieve effective radii of clouds particles, ice water content and optical depth of sounded clouds. The algorithm is also able to retrieve the water contents for the mixed-phase layers and this capability was tested on an altocumulus case of CLARE 2000.Les nuages jouent un rôle important dans l'évolution de l'atmosphère météorologique et dans le contrôle du climat. Or leur représentation paramétrique dans les modèles numériques de prévision météorologique et climatologique n'est toujours pas validée à ce jour. La préoccupation de la communauté scientifique internationale d'être à même de mieux contrôler à l'échelle globale l'effet radiatif des nuages a stimulé plusieurs programmes spatiaux mettant en œuvre une combinaison radar-lidar (CLOUDSAT/CALIPSO et EarthCare). De telles expériences spatiales ont besoin de démonstrateurs aéroportés tels que RALI (système synergique RAdar nuage - LIdar), qu'il s'agisse de la mise au point des algorithmes de traitement de données, ou de la validation des produits de la mission spatiale. Ainsi, le projet RALI vise le développement et l'exploitation d'une combinaison instrumentale radar-lidar aéroportée ou au sol, pour documenter les profils verticaux des propriétés microphysiques, dynamiques et radiatives des nuages glacés non précipitants. C'est dans ce cadre que s'inscrit cette thèse. Dans un premier temps, un modèle inverse reliant les paramètres de télédétection aux paramètres nuageux a été construit. Ce modèle permet de s'affranchir de la forme de la distribution dimensionnelle des particules; il sert de base à l'application de l'algorithme synergique radar-lidar. Celui-ci, prenant en compte la variation verticale de la concentration des particules nuageuses, a également été développé. Des tests de simulation ont été effectués afin de déterminer sa robustesse, sa précision et les conditions optimales d'application. Les résultas obtenus sur des cas d'expérimentations instrumentales (Clare'98, Carl'99 et Clare'2000), comparés à des mesures in-situ microphysiques, ont montré sa capacité à restituer le rayon effectif des particules nuageuses, le contenu en glace et l'épaisseur optique des nuages sondés. L'algorithme est également capable de restituer le contenu en eau des couches de phase mixtes et sa capacité a été testée sur un cas d'altocumulus de Clare'2000