长江中下游稀土元素的水环境地球化学特征

采用中子活化分析技术同步研究了稀土元素在长江干流中下游水体各要素中的含量分布及其赋存形态。结果表明，稀土元素在河水中以悬浮态为主，溶解态含量极微。溶解态在中下游各河段呈均匀分布，与不同地带的河流也基本一致。而悬浮态含量较高，变幅较大。各河段的悬浮物或沉积物中稀土元素含量相近，悬浮物与沉积物中相应各稀土元素含量也基本一致。各河段悬浮物与沉积物的稀土元素分布模式均为轻稀土富集、铕亏损型，各稀土元素赋存形态特征相似，均以结晶态为主，各形态所占比例的排序均为结晶态》有机结合态、铁锰氧化物态＞碳酸盐结合态＞＞可交换态。各稀土元素相对比较，中稀土元素Ｅｕ、Ｓｍ、Ｔｂ的结晶态较轻、重稀土的结晶态所占比例低、而其它态相反。

AQUATIC ENVIKONMENTAL GEOCHEMISTRY CHARACTERISTICS OF RARE EAKTH ELEMENTS IN THE MIDDLE-LOWER REAHCES OF CHANGJIANG(YANGTZI)RIVER

The contents and speciation of Rare Earth Elements(REEs)in the auqatic environ-ment of the middle-lower reaches of Changjiang River have been studied bv neutron activa-tion analysis(INAA).The results show that REEs mainly exist in suspended particles,while the dissolved contents are in extremely minute quantities, The dissolved contents ofREEs in water of the middle-lower reahces of Changjiang River are similar to other rivers,and consistent along Changjiang River. Contents of REEs in suspended particles vary in awide range. REEs in sediments and suspended matter are similar. The REE distributionpatterns in both sediments and suspended matter are the same, with light REE enrichementand Eu depletion. The speciation characteristics of REE in the sediments and suspendedmatter are quite similar with the amount in as follows:residual>>bound organic matter>bond to Fe-Mn oxides>bond to carbonates>>exchnageable. Compared with light and heavyREEs,the intermediated REEs(Eu,Sm,Tb)have relatively low percentages in the resid-ual form and high in the form bond to organic matter and Fe-Mn oxides.