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Atmospheric dust is a major component of the Earth System. The optical properties of dust and their roles in cloud nucleation processes have a major impact on Earth’s radiative budget and hydrological cycle. Dusts also take part in many biogeochemical cycles in surface waters of the oceans and on land through their capacity to supply key micronutrients (e.g. Fe, P) sustaining primary production. The aim of this thesis is to improve the understanding of dust cycle by creating new and innovative methods allowing to trace the source regions of dust and quantify their respective contributions. We developed a chromatographic method to isolate and analyze six isotopic systems (i.e. Pb, Nd, Sr, Zn, Cu, Fe) widely used to trace dust source areas. We optimized a new method for single, low-mass dust samples and, in doing so, we observed that the usual rock reference materials (RM) used to calibrate isotopic analysis were not representative of dust. In fact, there is little to no RM for dust and therefore, we set out to characterize precisely the isotopic signatures of two new dust reference materials, ATD and BCR-723. The latter two are representative of natural-like and urban-like dust that we propose now as new standards for atmospheric dust studies. We also investigated dust deposition, along a 250-km transect from the NE Antarctic coastline to the Princess Elisabeth Station area. Using dust samples collected from Sigma-2 passive samplers or isolated from snow samples, we determined the morphology, size distribution and chemical composition of the dust samples at the particle-scale using an automated Scanning Electron Microscope coupled to Energy Dispersive Spectroscopy (SEM-EDS). More than 5500 particles were analysed and the results showed that the grain-size distribution was, RésuméLes particules atmosphériques (PA) sont un composant majeur du système Terre. Leurs propriétés optiques ainsi que leur rôle au sein des processus de nucléation des nuages ont des impacts majeurs sur le budget radiatif et hydrologique de la terre. Les PA interviennent aussi dans de nombreux cycles biogéochimiques à la surface des océans ou sur terre grâce à leur capacité à fournir des nutriments clés (e.g. Fe, P) soutenant la production primaire. Le but de ce doctorat est d’améliorer la compréhension du cycle des PA en créant de nouvelles méthodes innovatrices permettant de tracer leurs origines et quantifier leurs contributions. Nous avons développé une nouvelle méthode chromatographique optimisée pour les PA afin d’analyser six systèmes isotopiques (i.e. Pb, Nd, Sr, Zn, Cu, Fe) largement utilisés pour tracer l’origine des PA. Afin de combler un manque crucial en terme de matériaux de référence (MR), nous avons quantifié deux nouveaux MR de PA, ATD et BCR-723 (représentatifs des milieux naturels et urbains) et nous les proposons pour toutes les futures études géochimiques de PA. Nous avons aussi étudié les dépositions atmosphériques le long d’un ‘transect’ de 250 km depuis la côte Antarctique jusqu’à la station Belge Princesse Elisabeth. Premièrement, nous avons réalisé des analyses morphologiques et chimiques à l’échelle de la particule à l’aide d’un Microscope Electronique à Balayage à dispersion d’énergie (MEB-EDS). Les analyses ont montré une distribution granulométrique, Doctorat en Sciences, info:eu-repo/semantics/nonPublished

Atmospheric mineral dust is intrinsically linked with climate. Although dust flux variability on glacial–interglacial timescales is well documented, Holocene dust records remain scarce. To fill this gap, we conducted elemental, isotopic and sedimentological analyses on a peat core from the Karukinka Natural Park in Tierra del Fuego. An 8000-year-old mineral dust record was extracted indicating three periods of elevated dust deposition: (i) 8.1–7.4 cal ka BP, (ii) 4.2 cal ka BP and (iii) 2.4–1.4 cal ka BP. The two oldest peaks are related to volcanic eruptions of the Hudson and Monte Burney volcanoes, respectively. The most recent dust peak, however, has a rare earth element and neodymium isotopic composition that resembles the geochemical signature of outwash plain sediments from the Darwin Cordillera. Since the timing of this dust peak corresponds to a period of glacier retreat between Neoglacial advances III and IV, we infer that Holocene aeolian dust fluxes in southern Patagonia are mostly driven by glacial sediment availability. Our results underline the important role of glaciers in producing aeolian dust in high-latitude regions, and they imply that the current retreat of glaciers worldwide may result in elevated atmospheric dust loads. Fil: Vanneste, Heleen. Centre National de la Recherche Scientifique; Francia. Université de Toulouse; Francia Fil: De Vleeschouwer, François. Université de Toulouse; Francia. Centre National de la Recherche Scientifique; Francia Fil: Bertrand, Sébastien. University of Ghent; Bélgica Fil: Martínez Cortizas, Antonio. Universidad de Santiago de Compostela; España Fil: Vanderstraeten, Aubry. Université Libre de Bruxelles; Bélgica Fil: Mattielli, Nadine. Université Libre de Bruxelles; Bélgica Fil: Coronato, Andrea Maria Josefa. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Austral de Investigaciones Científicas; Argentina Fil: Piotrowska, Natalia. Silesian University Of Technology; Polonia Fil: Jeandel, Catherine. Université de Toulouse; Francia Fil: Roux, Gaël Le. Université de Toulouse; Francia. Centre National de la Recherche Scientifique; Francia

info:eu-repo/semantics/published

Melting of the Greenland Ice Sheet is a leading cause of land-ice mass loss and cryosphere-attributed sea level rise. Blooms of pigmented glacier ice algae lower ice albedo and accelerate surface melting in the ice sheet���s southwest sector. Although glacier ice algae cause up to 13% of the surface melting in this region, the controls on bloom development remain poorly understood. Here we show a direct link between mineral phosphorus in surface ice and glacier ice algae biomass through the quantification of solid and fluid phase phosphorus reservoirs in surface habitats across the southwest ablation zone of the ice sheet. We demonstrate that nutrients from mineral dust likely drive glacier ice algal growth, and thereby identify mineral dust as a secondary control on ice sheet melting.