ABSTRACT

Twenty two samples of surface sediments were obtained by means of an Ekman Birge sampler during 1967–1989 in the East China Sea and the Yellow Sea area. Subsequent leaching with water, 6% acetic acid, 0.1 N HCl, and 30% H₂O₂ were done, followed by digestion with a mixture of mineral acids (HF, HNO₃ and HClO₄), in order to separate the chemical species, mainly of exchangeable ions, carbonate fraction, sulfide, organic metal fraction and mineral fraction. The concentrations of Ca, Mg, Sr, Ba, Cr, Ni, Mn, Fe, Al and Ti were determined for each fraction by multi-channel ICP emission spectrometry. The regional distribution of the total concentrations of the elements are summarized as follows: (i) Ca and Sr are higher at the edge of continental shelf, (ii) Mn, Ba and Cr are higher near the Changjiang mouth, and (iii) Mg, Al, Ti and Ni are relatively uniform. The behavior of alkaline earth elements in the acetic acid soluble fraction is explained by the contribution of carbonates to the sediments. High Mg/Ca ratios upto 3.5 in the hydrofluoric acid fraction of offshore sediments are ascribed to isomorphic ionic exchange of clay minerals.