MINERAL DUST ELEMENTAL COMPOSITION OVER THE LAST 220 KYR FROM THE EPICA-DOME C ICE CORE (EAST ANTARCTICA)

Mineral windblown aerosol (dust) represents a small fraction of the total mass of atmospheric aerosols. However, it may play an important role in climate and, in turn, it is itself sensitive to climatic changes.The investigation of the temporal variability of dust flux as well as the changes of its mineralogical composition within different climatic periods offers a unique way of assessing the source-related environmental changes, the variation in atmospheric circulation, and the potential influence of dust on biogeochemical cycles, for several key elements (such as Si and Fe). The mineral composition of dust found in ice cores is still poorly known, because few techniques are able to provide information on the chemical composition of the insoluble aerosol fraction, because of the very low mass of dust usually present in polar ice samples. Total volume of mineral content is provided by Coulter Counter measurements, and the dust record shows higher dust input during glacial periods than during interglacials (Delmonte et al., 2004). Sr and Nd isotopic tracers for identification of dust provenance to East Antarctica suggest southern South America as the dominant common source for dust in glacial periods of the late Pleistocene (Delmonte et al., 2004), whereas dust provenance during interglacials periods is still highly uncertain. Elemental composition of mineral dust from the Dome C ice core (75ø 06' S, 123ø 21' E) drilled in the framework of the European Project for Ice Coring in Antarctica (EPICA) is presented, showing measurements obtained by the Proton Induced X-ray Emission (PIXE) technique applied on insoluble atmospheric dust in ice cores. Within this work, substantial improvements to the experimental set-up and data processing have been made, compared to previously presented works on the first 2200 m of the EDC ice core, corresponding to about 220 kyr of climatic history (Marino et al., 2004; Ghermandi et al., 2003). The PIXE technique, based on X-ray spectrometry, allows direct measurements on filters of the insoluble dust fraction without sample pre-treatment, with analytical detection limits less than 1 ppb. The minimum required mass density of sample material on the filter is about 0.1 microg cm-2. Improvements made here allowed us to obtain accurate records of 8 major and minor crustal elements (Si, Al, Fe, Ti, K, Ca, Mg, Na). The data for these 8 elements, as well as their proportions as oxides, are shown for different climatic periods. Because O, Si, Al, Fe, Ti, K, Ca, Mg, Na are the principal constituents (99.90 %