长江口表层沉积物中稀土元素地球化学特征

Geochemical behaviors of rare earth elements in sediments of the estuary of Yangtze River

用电感耦合等离子体质谱法测定了2002年8～9月航次丰水期采集的长江口表层沉积物样品，对稀土元素（REEs）在沉积物的中含量分布、配分模式及其与某些常量矿物成份之间的相关关系进行了研究．结果表明，长江口表层沉积物中REEs含量在0．17μg／g（Lu）-78．9μg／g（Ce）之间，含量高低顺序为Ce〉La〉Nd〉Sm〉Yb〉Eu〉Tb〉Lu；用PAAS和世界平均页岩的REEs含量进行Ce、Eu异常值的计算结果表明，长江口沉积物中Ce和Eu均表现出轻微正异常；沉积物中REEs在轻稀土元素（LREE）富集的基础上，表现出中稀土元素（MREE）相对富集的特征，其中用PAAS标准化后MREE富集程度比用世界平均页岩标准化后的结果要明显．通过比较沉积物和悬浮颗粒物的分馏表征值、REEs含量和浓度变化范围等，认为长江口沉积物的主要来源是水体悬浮颗粒物．本文对REEs与Al2O3和Mn的相关性研究还发现，两者与重稀土元素（HREE）有较明显的正相关关系，其中Al2O3与HREE的线性相关性较好．

To assess the distribution pattern and the fraction during estuary mixing processes and fiver transportation, the concentrations of rare earth elements （REEs） in sediments of the estuary of Yangtze River, China, were measured using acid digestion and inductively coupled plasma mass spectrometry （ ICP MS）. As results, REEs contents in sediments are found in range of 0. 17μg/g（Lu） ～78.91xg/g（Ce）. In sediments the concentration level of REEs follows the order： Ce 〉 La 〉 Nd 〉 Sm 〉 Yb 〉 Eu 〉 rib 〉 Lu. The lack of any significant anomalies for Ce and Eu suggests that redox processes did not play important roles in redistribution of REEs. Normalized patterns of REEs in sediments by PAAS are dominated by a distinct convexity centered on Eu, which suggests an enrichment of MREE over both LREE and HREE. Plots of PAAS-normalized REEs data in sediments are similar to that of the residual fraction in suspended matter.