Distribution of rare earth elements and other high field strength elements in glacial meltwaters and sediments from the western Greenland Ice Sheet: Evidence for different sources of particles and nanoparticles
Distribution of rare earth elements and other high field strength elements in glacial meltwaters and sediments from the western Greenland Ice Sheet: Evidence for different sources of particles and nanoparticles
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DOI：
10.1016/j.chemgeo.2015.07.026
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发表时间：
2015-09
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
虽然全球变暖增加融水输入到海洋中，而鲜为人知的是高场强元素，如稀土和Y（REY），锆，铪，钍，和U在北极冰川融水和冰川河流的分布。我们研究了格陵兰冰盖（GRIS）西部的Kangerlussuaq地区的冰川融水和冰川河流，以及Isua地区的冰川湖泊及其融水流入。在0.2 μ m过滤的水样（“溶解”部分）、相应的过滤残留物（“颗粒”部分）和环境沉积物（包括来自全球资源信息系统表面上的融水池的冰尘）中测定了痕量元素浓度。我们还测量了“真正溶解”REY浓度在10 kDa的超滤样品从冰川喂养的沃森河页岩归一化（“SN”）REY模式的颗粒部分和环境沉积物（包括冰屑）是相当相似的当地太古代片麻岩，并显示积极EuSNanomalies。这排除了亚洲尘埃（不显示积极的EuSNanomalies）作为这些铝硅酸盐颗粒的可能来源，但表明当地太古代基底被侵蚀，目前被冰，水和风输送到GRIS前面和上面的沉积地点。与热带、温带和北方河流相比，所有0.2 μ m过滤的冰川河流都显示出非常不寻常的REYSN模式，并且相对于重REY，轻REY显著富集。对于冰川补给的沃森河，< 10 kDa的超滤液显示出比< 0.2 μ m的滤液低得多的REY浓度，这表明后者中> 99%的La和> 78%的Yb与纳米颗粒和胶体有关。虽然< 0.2 μ m-Eu的REYSN模式与颗粒部分和环境沉积物的REYSN模式非常相似，但它们缺乏EuSNanomalies，而来自GRIS表面上的融水池的< 0.2 μ m-Eu显示出与冰尘相似（但略小于）的EuSNanomalies。虽然来自融水池塘的水携带来自当地太古代来源的纳米粒子，但冰川河流中缺乏EuSNanomalies表明，它们的纳米粒子和胶体负载代表了从GRIS更深处重新动员的大气尘埃。这些尘埃大部分可能起源于亚洲东部，并显示出类似于后太古代上陆壳的REY分布，即，没有任何EuSnanomaly。因此，REY地球化学表明，这些北极融水中的颗粒和纳米颗粒/胶体来自不同的来源。
Although global warming increases meltwater input into the oceans, rather little is known about the distribution of high field strength elements such as the rare earths and Y (REY), Zr, Hf, Th, and U in arctic glacial meltwaters and glacial-fed rivers. We studied glacial meltwater and glacial-fed rivers from the Kangerlussuaq area and a glacial-fed lake and its meltwater inflow in the Isua area, both in the western part of the Greenland Ice Sheet (GRIS). Trace element concentrations were determined in 0.2 μm-filtered water samples (“dissolved” fraction), in the respective filter residues (“particulate” fraction) and in ambient sediments (including cryoconite from a meltwater pond on the surface of the GRIS). We also measured “truly dissolved” REY concentrations in a 10 kDa-ultrafiltered sample from glacial-fed Watson River.Shale-normalized (“SN”) REY patterns of the particulate fraction and ambient sediments (including cryoconite) are rather similar to those of local Archean gneisses and show positive EuSNanomalies. This rules out Asian dust (which does not show positive EuSNanomalies) as a possible source of these aluminosilicate particles, but suggests that local Archean basement is eroded and currently transported by ice, water and wind to the depositional sites in front of and onto the GRIS. All 0.2 μm-filtered glacial-fed rivers show very unusual REYSNpatterns in comparison to tropical, temperate and boreal rivers, and are significantly enriched in light relative to heavy REY. For glacial-fed Watson River, the < 10 kDa-ultrafiltrate shows much lower REY concentrations than the < 0.2 μm-filtrate, suggesting that > 99% of La and > 78% of Yb in the latter are associated with nanoparticles and colloids. Although the REYSNpatterns of the < 0.2 μm-filtrates are rather similar to those of the particulate fraction and ambient sediments, they lack any EuSNanomalies, whereas the < 0.2 μm-filtrates from a meltwater pond on the surface of the GRIS show positive EuSNanomalies similar to (but somewhat smaller than) the cryoconite. While the water from the meltwater pond carries nanoparticles derived from local Archean sources, the lack of EuSNanomalies in the glacial-fed rivers suggests that their nanoparticle and colloid load represents atmospheric dust that is remobilized from greater depth in the GRIS. Most of this dust probably originated from eastern Asia and shows a REY distribution similar to Post-Archean upper continental crust, i.e., lacks any EuSNanomaly. Hence, REY geochemistry suggests that the particulates and the nanoparticles/colloids in these arctic meltwaters are derived from different sources.