Study of Long Term (10 exp 3 -10 exp 4 Y) Elemental Migration in Saturated Clays and Sediments

摘要

A 5m sediment core from L. Lomond, in which a well defined band of marine sediment resulting from the Flandrian marine transgression is present, was extensively analysed by INAA, XRF and alpha -spectrometric techniques. Approximately 10 exp 3 concentration data points for elements including Na, K, As, Br, I, La, Sm, Sc, Cr, Fe, Co, Rb, Sb, Cs, Ce, Eu, Tb, Lu, Hf, Ta, U, Th and Ra are presented. From this large data set, some generalisations on the geochemistry of particular groups of elements (on a periodic table classification) are obtained. In addition, sorption data for Cs, Sr, Ce, Co, I, Tc and Np onto bulk samples of lacustrine and marine sediment were measured and analysed in terms of the expected speciation of these elements under experimental conditions. Using simple models of element remobilisation by diffusive and advective processes it is shown that the elemental profiles observed in-situ are not readily explained by variations in measured sorption. Of particular relevance is the apparent resistance of high I and Br concentrations in the marine layer to post depositional remobilisation. Possible explanations for the discrepancies between calculated and observed profiles are discussed and detailed proposals are advanced for a more rigorous investigation of these sediments. (Atomindex citation 15:056991)