Rare earth elements in the water column of Lake Vanda, McMurdo Dry Valleys, Antarctica
Rare earth elements in the water column of Lake Vanda, McMurdo Dry Valleys, Antarctica
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DOI：
10.1016/s0016-7037(01)00861-4
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发表时间：
2002-04-01
影响因子：
5
通讯作者：
Green, WJ
中科院分区：
文献类型：
--
作者：
De Carlo, EH;Green, WJ
我们提供了南极洲万达湖水的组成数据。南极洲麦克默多干谷的万达和其他湖泊的特点是封闭的盆地、永久的冰盖和深咸水。由于它们的原始性质和相对简单的生物地球化学系统，它们为痕量金属循环的研究提供了模式系统。位于莱特谷的万达湖只有一个输入，即玛瑙河流，没有输出。对湖水的输入是通过升华几乎永久的冰帽来平衡的，冰帽在南半球夏季只在海岸线附近破裂。利用电感耦合等离子体质谱分析了在痕量元素清洁条件下采集的水体中溶解稀土元素(REE)和总稀土元素含量。深度剖面的特征是地表水中溶解的稀土元素浓度较低(La、Ce和Lt；15 Pm)，随着深度的增加(La，70 Pm；Ce，20 Pm)略有增加，接近55米，这是淡水含氧水域的极限。在此深度以下，严格的三价稀土元素(如La，5 nm)浓度急剧增加，氧化还原敏感型Ce(2.6 nm)在60-62-m深度出现次最大值。在稍深的深度，观察到更尖锐的Ce最大值，浓度超过11海里米，在67米深，紧邻缺氧区上方。这里报告的水中稀土元素浓度类似于以前报告的海洋氧/缺氧界面的50倍，据我们所知，是在天然氧/缺氧界面观察到的最高水平。极大稀土元素出现在稳定和温暖的咸水中。在硫化物底水中，所有稀土元素的浓度都急剧下降。万达湖的氧化还原跃层主要受浓度梯度驱动的扩散过程和溶解物质的垂直迁移控制。此外，由于湖泊的超低营养性质限制了有机相作为金属载体的潜力，金属氧化物涂层和硫化物相似乎在很大程度上控制了微量元素的分布。我们讨论了稀土元素的循环与氧化还原反应和对粘土颗粒上的铁氧化物和锰氧化物涂层的竞争清除的作用，以及它们在缺氧/氧化界面附近的还原溶解释放的作用。版权所有(C)2002爱思唯尔科学有限公司。
We present data on the composition of water from Lake Vanda, Antarctica. Vanda and other lakes in the McMurdo Dry Valleys of Antarctica are characterized by closed basins, permanent ice covers, and deep saline waters. The meromictic lakes provide model systems for the study of trace metal cycling owing to their pristine nature and the relative simplicity of their biogeochemical systems. Lake Vanda, in the Wright Valley, is supplied by a single input, the Onyx River, and has no output. Water input to the lake is balanced by sublimation of the nearly permanent ice cap that is broken only near the shoreline during the austral summer. The water column is characterized by an inverse thermal stratification of anoxic warm hypersaline water underlying cold oxic freshwater.Water collected under trace-element clean conditions was analyzed for its dissolved and total rare earth element (REE) concentrations by inductively coupled plasma mass spectrometry. Depth profile, are characterized by low dissolved REE concentrations (La, Ce, < 15 pM) in surface waters that increase slightly (La, 70 pM; Ce, 20 pM) with increasing depth to similar to 55 m, the limit of the fresh oxic waters. Below this depth, a sharp increase in the concentrations of strictly trivalent REE (e.g., La, 5 nM) is observed, and a submaximum in redox sensitive Ce (2.6 nM) is found at 60- to 62-m depth. At a slightly deeper depth, a sharper Ce maximum is observed with concentrations exceeding 11 nM at a 67-m depth, immediately above the anoxic zone. The aquatic concentrations of REE reported here are similar to 50-fold higher than previously reported for marine oxic/anoxic boundaries and are, to our knowledge, the highest ever observed at natural oxic/anoxic interfaces. REE maxima occur within stable and warm saline waters. All REE concentrations decrease sharply in the sulfidic bottom waters. The redox-cline in Lake Vanda is dominated by diffusional processes and vertical transport of dissolved species driven by concentration gradients. Furthermore, because the ultraoligotrophic nature of the lake limits the potential for organic phases to act as metal carriers, metal oxide coatings and sulfide phases appear to largely govern the distribution of trace elements. We discuss REE cycling in relation to the roles of redox reactions and competitive scavenging onto Mn- and Fe-oxides coatings on clay sized particles in the upper oxic water column and their release by reductive dissolution near the anoxic/oxic interface. Copyright (C) 2002 Elsevier Science Ltd.