| Radiaochemical procedures by which prepare radioactive multitracer solutions, removal mechanisms of metal elements from seawater and MOssbauer spectroscopy in marine samples were studied in the present work. Main results are as follows:1.We established "multitracer" , a new versatile radiotracer technique, for simultaneous tracing of a number of elements in various chemical , environmental, and biological systems. Metal foil targets (typically Au, Ag, Ge, Cu and Fe) are irradiated with C, N, or 0 ions accelerated up to 135 Me V/nucleon by RIKEN Ring Cyclotron. Radiochemical procedures have been developed to remove the target material leaving the nuclides as Multitracer solutions containing various radionuclides of Be, Na, Mg, K, Ca, Sc V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Se, Br, Rb, Sr, Y, Zr, Nr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Te, I, Ba, Ce, Pm, Eu, Gd, Tb, Tm, Yb, Lu, Hf, W, Re, Os, Ir, Pt, and Hg. Multiracers enable efficient tracing of a number of elements, and comparison of their behavior under strictly identical experimental conditions. Such features will be demonstrated by means of an example of application to a model experiment for the study of removal mechanism of various elements from the ocean.2 . Using radioactive multitracers produced by RIDEN 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(Kads) of Mg, Sc, V, Mn, Fe, Co, Ni, Zn, Ca, 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 can be summarized as follows: hydrated ferric oxide > deep-sea sediment > montmorillinite > near-shore sediment > kaolinite. The observed relationships between log Lads 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.3.The chemical states of iron in near-shore, deep-sea sediments and manganese nodule were investigated by means of n'Fe Mossbauer spectroscopy in combination with selective and non-selective chemical leachings. As far as a limited number of the sediments analyzed are concerned, Mossbauer spectra of near-shore sediments consist of high-spin paramagnetic ferrous(δ=1. 13mm/s ,ΔEq=2.65mm/s) and paramagnetic ferric(δ=0. 35mm/s, ΔEq=0. 64mm/s)components, while those of deep-sea sediments are composed of high-spin paramagnetic ferrous, paramagnetic ferric and magnetic ferric (δ~ 0. 4mm/s, H~ 510 KG) components. The Fe2V Fe3+ ratios of deep-sea sediments are much smaller than those in near-shore sediments, while the total concents of iron in the former are much higher than those in the latter. This is principally due to the high contents of authigenic ferric oxides in deep-sea sediments. Further, in the aluminosilicate fraction, the Fe2+/ Fe3* ratios of deep-sea sediments are also smaller than those of near-shore sediments. This is probably attributed to high contents of clay minerals and authigenic aluminosilicates in deep-sea sediments relative to near-shore ones. The magnetic components in deep-sea sediments are attributable to hematite, magnetite and/or maghematite. Mossbauer spectra of manganese nodule consist of high-spin paramagnetic ferrous(δ=1. lOmm/s , ΔEq=2.62mm/s) and paramagnetic ferric(δ=0. 35mm/s, ΔEq=0. 68mm/s). The former is much more pronounced in the spectrum of the sample after leaching. The ferrous component in the manganese nodule are shown to originate in terrigeous materials transported from lands through the atmosphere.4. The chemical states and relative concentrations of iron in the sediments from the Zhujiang River mouth, the northeastern South China Sea and Nansha sea area are studies by means of 57Fe Mossbauer spectroscopy. Mossbauer spectra of near-shore sediments consist of high-spin paramagnetic ferrous(δ=1.12mm/s, Δ...
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