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Etude de la composition chimique de la basse atmosphère des régions cotières antarctiques (station française de Dumont d'Urville)- Antarctique

Abstract : The geographical and meteorological conditions of polar regions make them of the utmost interest for many environmental studies. Located far away trom continents ( where local sources like wind blow dust, biospheric emissions from vegetation and soils or anthropegenic sources dominate) Antarctic regions have been recognized as having the cleanest atmospheric environment of Southern hemisphere. ln this context, coastal Antarctic areas are particulary well adapted for studying the biogenic emissions from the circumpolar ocean. At the end of 1990, a european program was etablished for the thorough tropospheric chemistry study at the french station (Dumont d' Urville) in Antarctica.The fust part of our study concerned the potential contamination of our site by the base (Dumont d'Urville). It should that the humain activity has a low impact on our sampling, while nearby pingouins rookeries were emitting large amounts of NH3, NH4+, C2O42-, Ca2+, K+, in the atmosphere. The study of atmospheric sulphur species (sulfate and methanesulfonate) showed that sea salt aerosols are fractionned during the winter. The sulfate concentrations in these aerosols are depleted compared to sea water concentrations. Moreover, the Cl-/ Na + ratio are higher in these fractionned aerosols than in sea water. The inter annual variability of atmospheric sulfate concentrations showed a perturbation during the 1991-1992 austral summer. This perturbation is attribued to the gravitational sedimentation of the volcanic plume emitted by the Cerro Hudson eruption. The seasonnality of methanesulfonic acid and non sea salt sulfate is linked to the biological primary productivity of the austral ocean. Also, we demonstrated that the differences in atmospheric concentrations between Dumont d'Urville, Mawson and Georg von Neumayer could be explain by differences in the primary productivity in the sectors of the polar ocean influencing each station. Finally, the atmospheric concentrations of nitrogen species (NH4+, N03-, HN03) suggest that ammonium concentrations measured at Mawson (67.6°S, 62.5°E) are certainly contamined by local rookeries. The sedimentation of Polar Stratospheric Cloud is probably responsable for the saisonnality we observed in the nitrogen oxydes concentrations measured in coastal antarctic areas.
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François Ducroz. Etude de la composition chimique de la basse atmosphère des régions cotières antarctiques (station française de Dumont d'Urville)- Antarctique. Ingénierie de l'environnement. Université Joseph-Fourier - Grenoble I, 1996. Français. ⟨tel-00766849⟩

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