Behavior of rare earth elements and yttrium during simulation of arctic estuarine mixing between glacial-fed river waters and seawater and the impact of inorganic (nano-)particles
Behavior of rare earth elements and yttrium during simulation of arctic estuarine mixing between glacial-fed river waters and seawater and the impact of inorganic (nano-)particles
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DOI：
10.1016/j.chemgeo.2016.06.001
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发表时间：
2016-11
期刊：
影响因子：
3.9
通讯作者：
Nathalie Tepe;M. Bau
中科院分区：
文献类型：
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作者：
Nathalie Tepe;M. Bau
河流是海洋中许多微量元素的主要来源。由于气候变化，越来越多的冰川融水在受到河口过程的影响后进入海洋。虽然高场强元素，如稀土元素和钇（REY）的行为已被深入研究，在热带，温带和北方河口，鲜为人知的是北极河口混合冰川喂养的河流沃茨，是穷人的有机纳米粒子和胶体（NPC），但丰富的无机NPC。在这里，我们提供的第一个数据集从河口混合实验与冰川喂养的河流沃茨和海水。冰川补给的河水端元源自冰岛南部（2010年和2013年抽样）和西格陵兰（2013年抽样）;这些端元分别富含NPC和（玻璃状）火山灰和超细岩石粉的较大颗粒，对于混合实验，将0.2 μ m过滤的冰川补给河水与海水以不同比例混合，以覆盖河口低盐度到高盐度条件的全部范围。所有2010年淡水端元的REY浓度（由于其高NPC负载）高于各自的海水端元，而2013年淡水端元的轻REY浓度较高，但较低的重REY浓度（由于显着较少的NPC）。微量海水的混合物（5%和10%海水（SW）混合物，即盐度分别为~ 1.7 psu和~ 3.4 psu）已经对REY浓度和REY特征产生了强烈的影响。在所有实验中，大量的REY（例如，高达98.2%的Nd和98.2%的Yb）在非常低的盐度下被去除。然而，在中等至高盐度，REY从聚集的NPC发生再活化，如果NPC丰富的河流沃茨中使用的实验，而如果端元是穷人的NPC，REY混合几乎保守。REY的去除取决于冰川河流沃茨中NPC的含量;富含NPC的河水比NPC含量较低的河水显示出更大的REY去除率。在低盐度条件下REY浓度最初下降后，来自格陵兰的冰川河水实验表明，重REY混合几乎保守，但轻REY再次从聚集的NPC中重新动员。我们的结果表明，由岩粉（格陵兰岛）和火山灰（冰岛）组成的聚集NPC可能会在河口过程中导致不同的微量元素行为。然而，所有的实验表明，在河口混合类似的Y-Ho分馏，表明颗粒的实际类型是不是一个主要的约束Y-Ho的行为，而是颗粒表面的可用性。河口过程可能会导致负Ce异常REY在较高的盐度，如果Ce（IV）化合物的溶解度低的再活化过程中的发展（纳米）颗粒负载。然而，如果只有Ce（III）存在，例如在新鲜的镁铁质火山灰中，则不会发生Ce与其三价REY邻居的分馏。
Rivers are the major source of many trace elements to the oceans. As a consequence of climate change, increasing volumes of glacial meltwater enter the oceans after being affected by estuarine processes. Although the behavior of high field strength elements such as the rare earth elements and yttrium (REY) has been intensively studied in tropical, temperate and boreal estuaries, little is known about arctic estuarine mixing of glacial-fed river waters that are poor in organic nanoparticles and colloids (NPCs), but rich in inorganic NPCs. Here we provide the first data set from estuarine mixing experiments with glacial-fed river waters and seawater. The glacial-fed river water endmembers originate from southern Iceland (sampled in 2010 and 2013) and from West Greenland (sampled in 2013); these endmembers are rich in NPCs and larger particles of (glassy) volcanic ash and of ultra-fine rock flour, respectively.For the mixing experiments, 0.2 μm-filtered glacial-fed river water was mixed with seawater in different ratios to cover the full range of estuarine low- to high-salinity conditions. All 2010 freshwater endmembers show higher concentrations of individual REY (due to their high NPC load) than the respective seawater endmember, whereas the 2013 freshwater endmembers have higher light REY, but lower heavy REY concentrations (due to significantly less NPCs). Admixture of minute amounts of seawater (5% and 10% seawater (SW) admixture, i.e. salinities of ~ 1.7 psu and of ~ 3.4 psu, respectively) already has a strong impact on REY concentrations and REY signatures. In all experiments, a large amount of REY (e.g., up to 98.2% of Nd and 98.2% of Yb) is removed at very low salinities. At intermediate to high salinities, however, remobilization of REY from aggregated NPCs occurs if NPC-rich river waters are used in the experiments, whereas if the endmember is poor in NPCs, the REY mix almost conservatively. The REY removal is dependent on the amount of NPCs present in the glacial-fed river waters; NPC-rich river water shows larger REY removal than NPC-poorer river water. After the initial drop in REY concentrations under low-salinity conditions, the experiment with glacial-fed river water from Greenland reveals that heavy REY mix almost conservatively, but light REY are again remobilized from aggregated NPCs. Our results suggest that aggregated NPCs composed of rock flour (Greenland) and volcanic ash (Iceland) may cause different trace element behavior during estuarine processes. However, all experiments show similar Y-Ho fractionation during estuarine mixing, indicating that the actual type of particle is not a major constraint on Y-Ho behavior, but rather the availability of particle surfaces. Estuarine processes may cause the development of negative Ce anomalies during remobilization of REY at higher salinity if Ce(IV) compounds of low solubility are present in the (nano-)particle load. However, if only Ce(III) is present, such as in fresh mafic volcanic ash, no fractionation of Ce from its trivalent REY neighbors occurs.