Retardation of dissolved radiocarbon through a carbonated matrix

Spiked solutions (14C and 3H) were passed through two columns, one filled with silica and one with a mixture of silica and carbonate sand. Significant delay of 14C vs. 3H appeared in the second material and leads to a reduction of the relative flow rate which reaches 40%. Three types of effects causing modifications of the 14C transfer are analysed: (i) flow rate, (ii) sediment aging (iii) solution chemical composition and load. The reside with respect to water is governed by a linear process (assuming a constant number of reacting sites on the matrix) and kinetic process (where mass transfer effects are significant). It is also shown that much less than one mono-molecular layer of solid carbonate is involved and a distribution coefficient was estimated for these dynamic runs. Under field conditions, the interaction between 14C species (in the mobile and in the stationary phases) make ages obtained by 14C overestimated.

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