Rare earth elements in pore waters of marine sediments
Rare earth elements in pore waters of marine sediments
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DOI：
10.1016/j.gca.2003.09.012
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发表时间：
2004-03-01
影响因子：
5
通讯作者：
McManus, J
中科院分区：
文献类型：
--
作者：
Haley, BA;Klinkhammer, GP;McManus, J
从秘鲁附近的一个地点和加利福尼亚州边缘的三个地点采集了25厘米厚的沉积物，在上面的孔隙水中测量了稀土元素。孔隙水的稀土元素含量高于海水，且在浓度和归一化模式上都呈现出系统的岩心下移变化。根据这些分析和与测定的其他化学形态(溶解的Fe、Mn、Ba、氧、硝酸盐、磷酸盐)的比较，认为孔隙水稀土可分为三类：铁源的、POC源的和氧化铈的。来自铁源的稀土元素出现在缺氧的地方；它们具有独特的“中稀土(MREE)富集型”模式。这一来源的浓度如此之高，以至于它们主导了铁氧化物还原带中的稀土元素趋势。来自POC源的通量的净结果是重稀土(HREE)相对于轻稀土(LREE)的相对富集，反映了POC的再矿化和与DOC的络合。一种常见的“线性”稀土元素模式，在氧化和缺氧沉积物中都可以看到，与这种POC来源有关，以及在秘鲁遗址的表层沉积物中看到的“HREE富集型”模式。总体而言，孔隙水结果表明，锰氧化物不是海洋中稀土的重要载体。提出了一个稀土生物地球化学模型，该模型试图协调稀土在海洋水柱和沉积物柱中的行为。该模型认为，POC、Fe-氧化物和Ce-氧化物来源可以解释从含氧海水到缺氧孔隙水环境中稀土元素的浓度分布和相对丰度模式。该模型也与我们的观察结果一致，即在任何氧化还原条件下，孔隙水的“Ce异常”都不超过1。版权所有(C)2004爱思唯尔有限公司。
The rare earth elements (REES) were measured in pore waters of the upper similar to25 cm of sediment from one site off Peru and three sites on the California margin. The pore water REE concentrations are higher than sea water and show systematic down core variations in both concentration and normalized pattern. From these analyses and from comparison to other chemical species measured (dissolved Fe, Mn, Ba, oxygen, nitrate, phosphate), it is suggested that pore water REEs can be grouped into three categories: those that are from an Fe-source, those that are from a POC-source, and cerium oxide. REES from the Fe-source appear where anoxia is reached; they have a distinctive "middle-REE (MREE) enriched" pattern. The concentrations in this source are so elevated that they dominate REE trends in the Fe-oxide reduction zone. The net result of flux from the POC-source is relative enrichment of heavy-REEs (HREEs) over light-REEs (LREEs), reflecting remineralizing POC and complexation with DOC. A common "linear" REE pattern, seen in both oxic and anoxic sediments, is associated with this POC-source, as well as a "HREE enriched" pattern that is seen in surficial sediments at the Peru site. Overall, the pore water results indicate that Mn-oxides are not an important carrier of REES in the oceans.A REE biogeochemical model is presented which attempts to reconcile REE behavior in the water and sediment columns of the oceans. The model proposes that POC, Fe-oxide and Ce-oxide sources can explain the REE concentration profiles and relative abundance patterns in environments ranging from oxic sea water to anoxic pore water. The model is also consistent with our observation that the "Ce-anomaly" of pore water does not exceed unity under any redox condition. Copyright (C) 2004 Elsevier Ltd.