Multitracer Study on Removal Mechanisms of Metal Elements from Seawater.

Using radioactive multitracers produced by RIKEN Ring Cyclotron, the adsorption of metal elements on hydrated ferric oxide, marine sediments (deep-sea and near-shore sediments) and clay minerals (montmorillonite 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 K ads for each element can be summarized as follows : hydrated ferric oxide > deep-sea sediment > montmorillonite/near-shore sediment/kaolinite. The observed relationships between log K ads and the logarithm of the mean oceanic residence time indicate that adsorption of metal elements on marine particulate materials plays an important role in their removal from seawater.