MULTITRACER STUDY ON REMOVAL MECHANISMS OF METAL ELEMENTS FROM SEAWATER

Using radioactive multitracers produced by RIKEN Ring Cyclotron, the a dsorption of metal elements on hydrated ferric oxide, marine sediments (deep-sea and near-shore sediments) and clay minerals (montmorillonit e and kaolinite) from artificial seawater was studied. The adsorption coefficients (K-ads) Of Mg, Sc, V, Mn, Fe, Co, Ni, Zn, Ga, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, In, Sn, Eu, Gd, Tb, Tm, Yb, Lu , Hf, Re and Hg were determined. The order of Kads for each element ca n be summarized as follows: hydrated ferric oxide > deep-sea sediment > montmorillonite/near-shore sediment/kaolinite. The observed relation ships between log K-ads and the logarithm of the mean oceanic residenc e time indicate that adsorption of metal elements on marine particulat e materials plays an important role in their removal from seawater.