The D.C. conductivity of natural ice generally shows a strong correlation with the acidity of the meltwater sample. This method was successfully applied by Hammer (1) to detect debris of volcanic eruptions recorded in Greenland ice cores. In this paper we study several conductivity profiles for antarctic ice cores (Vostok and South Pole stations) in relation with a comprehensive study of soluble species. Our profiles revealed an important "double spike" on both conductivity and sulfuric acid record for snow deposited during the "Tambora years (1815)'' which is used as a statigraphic marker. Among the three acids (H2SO4, HCl and HNO3) usually present in the ice HCl and HNO3 seem to be more effective than H2SO4 on the conductivity background. In addition it is suggested a negative effect of aluminosilicates. These results suggest that impurities are located at grain boundaries where the pH can reach very low values. This assumption is in agreement with the conductivity model previously proposed by Wolff and Paren (2)
Research is considered as a major component of innovation and a key to the development of modern societies. However, fundamental research, which essentially aims at improving our understanding of Nature, is often questioned about its specific role. In this paper, arguments of ‘general interests’ in support of fundamental research are presented to contribute to the science-policy debate. Beyond a notable return on investment, now acknowledged by most economists, a number of positive societal impacts of fundamental research can be underlined. Fundamental research helps society as a whole, as well as individual firms, to keep options, possible scenarios and choices open (e.g. in relation with sustainable development), to maintain a good capability for top-level scientific expertise, to develop conditions favourable to scientific and technological breakthroughs, to ensure training at the highest possible level and also to guarantee access to, and free circulation of, the most valuable information. Finally, fundamental research may contribute to a better structural link between science and society.
The 234U/238U disequilibrium observed in nature has been previously interpreted by means of four models based on the properties of α-recoil nuclei and on the transport of uranium isotopes by natural waters. As aqueous dissolution of minerals can potentially dilute such disequilibrium by releasing large amounts of 238U, we tentatively evaluate the ability of these models to quantitatively account for the disequilibrium within different scenarios of aqueous corrosion. We show that three of the models (ejection of recoil nuclei and derived models) require very low (and unlikely) dissolution rates while the last one (change in valence state), which does not depend on the dissolution rates, seems plausible although it has not been particularly emphasized in recent works.
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