Trace elements variations in polar ice during the late quartenary with special emphasis on cosmic fallout

The determination of trace elements in deep polar ice cores provides important environmental information concerning natural sources, long-range transport and deposition processes of the aerosol during the late Quaternary (Iast few hundred thousands years). ln this work, we have measured various trace elements (Li, Mg, V, Cr, Mn, Co, Cu, As, Rb, Sr, Cd, Ba, Ir, Pt, Hg (including MeHg and Hg2+), Pb (including Pb isotopes), Bi and U) in various sections of three deep ice cores which were drilled in Antarctica and Greenland as a part of international programmes: the Dome C/EPICA ice core (past -220 kyr), the Vostok ice core (past -410 kyr) and the GRIP ice core (past -100 kyr). The analyses were performed by Inductively Coupled Plasma Sector Field Mass Spectrometry, Thermallonization Mass Spectrometry and Inductively Coupled Plasma Time of Flight Sector Field Mass Spectrometry, in clean room conditions. The results obtained for Ir and Pt shows evidence of the past fallout of vaporization and re-condensation products of meteoroids, the "meteoric smoke", to the polar ice caps. The meteoric smoke influx was used to estimate the past accretion rate of interplanetary dust particles to the Earth and to identify ancient changes in the Antarctic atmospheric circulation such as an enhanced subsidence onto the East Antarctic plateau during cold climatic stages.