Abstract:

Remobilization and accumulation mechanisms of iodine in marine sediments, which are divided into several geochemical environment, are studied. The result shows that iodine is characteristically rich in organic fractions of the sediments on the bottom of bay and pelagic sediments. However, it may be associated with oxyhydroxide and adsorptive phase in a highter percentage at the continental shelf and hemipelagic sediments. The environmental characteristics of remobilization of iodine in surficial sediments are similar to that of iron , that is, it is remobilized on anoxic conditions and converted into solid phases when it is in oxic environments, though the iodine does not act as the electron acceptor. The processes of adsorption and oxidation are responsible for the value of It/Corg in excess of that of planktonic materials other than the organic fraction in surficial sediments. It is a comprehensive effect of organism decomposition, oxyhydroxide reduction, paniculate adsorption and pore water diffusion on decrease of ratio of iodine to organic carbon with increasing depth in sedimentary column. The diffusive and depositional fluxes of iodine are of the same magnitude, which could be the cause for the poor iodine contents in sedimentary rocks. Based on the calculation and discussion, a new model for the remobilization and accumulation of iodine in marine sediments is set up.

Key words: Southern Ocean, sediment, iodine