Emission de poussière en Patagonie
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L’article “New constraints on elemental and Pb and Nd isotope compositions of South American and Southern African aerosol sources to the South Atlantic Ocean.” par R. Khondoker, D. Weiss, T. van de Flierdt, M. Rehkämper, K. Kreissig, B.J. Coles, S. Strekopytov, E. Humphreys-Williams, S. Donga, A. Bory, V. Bout-Roumazeilles, P. Smichowski, P. Cid-Agüero, M. Babinski, R. Losno, F. Monna vient d’être publié dans Chemie der Erde / Geochemistry. 2018, 78, 372-384.
L’étude dirigée par Roulin. Khondoker et Dominik Weiss vise à mieux caractériser chimiquement les aérosols anthropiques et naturels émis en Amérique du Sud et en Afrique australe. En effet, il est nécessaire d’aborder cette question de l’origine des aérosols afin de mieux comprendre le rôle des métaux dans les cycles biogéochimiques de la partie australe de l’océan Atlantique. Les échantillons qui intègrent cette nouvelle base de données ont différentes origines: poussières au bord des routes à Buenos Aires, lichens de Johannesburg, sols de Patagonie, cendres volcaniques de la ceinture andine, aérosols de São Paulo…
Abstract: Improving the geochemical database available for characterising potential natural and anthropogenic aerosol sources from South America and Southern Africa is a critical precondition for studies aimed at understanding trace metal controls on the marine biogeochemical cycles of the South Atlantic Ocean. We here present new elemental and isotopic data for a wide range of sample types from South America and Southern Africa that are potentially important aerosol sources. This includes road dust from Buenos Aires and lichen samples from Johannesburg, soil dust from Patagonia, volcanic ash from the Andean volcanic belt, and aerosol samples from São Paulo. All samples were investigated for major (Al, Ca, Fe, Mg, Na, K, Mn) and trace element (Cd, Co, Cr, Cu, Ni, Pb, REE, Sc, Th, Y, V, Zn) concentrations and Nd and Pb isotopic compositions. We show that diagrams of 208Pb/207Pb vs. εNd, 208Pb/207Pb vs. Pb/Al, 1/[Pb], Zn/Al, Cd/Al, Cu/Al, and εNd vs. Pb/Al, and 1/[Nd] are best suited to separate South American and South African source regions as well as natural and anthropogenic sources. A subset of samples from Patagonia and the Andes was additionally subjected to separation of a fine (< 5 μm) fraction and compared to the composition of the bulk sample. We show that differences in the geochemical signature of bulk samples between individual regions and source types are significantly larger than between grain sizes. Jointly, these findings present an important step forward towards a quantitative assessment of aeolian trace metal inputs to the South Atlantic Ocean.