RELEASE KINETICS AND CONCENTRATION PROFILE OF DISSOLVED SILICON IN COMPACTED SEDIMENTS

The kinetics of release of dissolved silicon from river sediments unde r close to natural conditions have been studied on the basis of a semi -infinite diffusion model taking into account the dissolution of the s upport. A new theoretical framework suitable for the description and m odelling of such processes has been developed and the numerical soluti on compared with the asymptotic behaviour at short times. The dynamics of the concentration profile of dissolved silicon in the sediment pha se has been calculated, and by adjusting the model parameters to the e xperimental data on concentration profiles measured in a natural sedim ent and a fluvarium channel bed, reliable estimates for the diffusion coefficient and generation rate constant have been obtained.