南大西洋中脊表层沉积物中稀土元素的含量及分布模式分析

摘要

以HNO3_H2 O2_HF为消解体系,对南大西洋中脊16个站位表层沉积物进行消解,应用电感耦合等离子体质谱测定了沉积物中稀土元素( Rare earth elements,REE)的含量,并分析了稀土元素的分布特征。结果表明,微波消解_ICP_MS方法测定稀土元素,各元素的线性关系良好(r=0.9997~1.0000),检出限可达ng/L,精密度好、准确度高,相对标准偏差(RSD, n=3)不大于3.0%,相对误差在6.0%以内。16个站位沉积物样品中稀土总量(ΣRE)变化范围为37.25~134.77μg/g,轻重稀土元素含量比值( LRE/HRE)的变化范围是0.61~1.70,平均值为1.27,沉积物中富集轻稀土略明显；从稀土配分模式看出,各个站位REE分布模式基本一致,轻重稀土元素之间有明显的分馏；不同来源沉积物中稀土元素分布模式类似,陆地和海洋沉积物稀土存在稍微差异；沉积物中δEu和δCe均出现负异常,说明了稀土元素主要是来自于海水。本研究分析了南大西洋中脊稀土元素的含量和分配规律,为深入研究大西洋中稀土元素的分布提供技术支撑和参考数据。%A microwave digestion system was preparation for the digestion of the sediment samples of 16 stations in the Southe mid_Atlantic ridge by using HNO3_H2 O2_HF as the digestion reagent. The rare earth elements ( RE ) in sediments were determined by inductively coupled plasma mass spectrometry, and distribution characteristics of rare earth elements were studied. The microwave digestion_ICP_MS method was used for the determination of rare earth elements with a good linear relationship ( r=0 . 9997-1 . 0000 ) for each element. The detection limit reached ng/L level, the relative standard deviation ( RSD, n=3 ) was less than 3% and the relative error was 6%. The total amount of rare earth elements (ΣRE) in sediment samples from 16 stations varied in the range of 37. 25-134. 77 μg/g, the ratio range of light RE/heavy RE ( LRE/HRE) was 0 . 61-1 . 70 , the average value was 1 . 27 , and the enrichment of light rare earth elements in sediments was slightly obvious. The RE distribution patterns were basically the same in each station with obvious fractionation between LRE and HRE. The RE distribution patterns were also similar in sediments from different sources with slightly difference between terrestrial and marine sediments. The δEu and δCe in the sediments had negative anomaly which showed that the rare earth elements in sediments came from the seawater. This study first analyzed the content and distribution of rare earth elements in the southern Atlantic, providing data and technical support for further study of the distribution of rare earth elements in the Atlantic.