Importance of vertical geochemical processes in controlling the oceanic profiles of dissolved rare earth elements in the northeastern Indian Ocean
Importance of vertical geochemical processes in controlling the oceanic profiles of dissolved rare earth elements in the northeastern Indian Ocean
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DOI：
10.1016/s0012-821x(02)01027-0
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发表时间：
2003-01-10
影响因子：
5.3
通讯作者：
Alibo, DS
中科院分区：
文献类型：
--
作者：
Nozaki, Y;Alibo, DS
在孟加拉湾和安达曼海获得了溶解稀土元素（REE）的垂直剖面。孟加拉湾各深度的稀土元素含量在印度洋中最高。这是由于最终的恒河，雅鲁藏布江和伊洛瓦底江的大量流出，但溶解的稀土元素通量的表面沃茨单独不能解释整个水柱的大型和近恒定的稀土元素富集。下伏扇沉积物不是溶解REE（III）的源，而是汇。在深水沃茨中没有过量的Ra-228表明，在这些地区，来自斜坡沉积物的溶解稀土元素的横向输入也很小。部分（<0.3%）溶解的碎屑颗粒，这是由河流和侧表面流，随后通过水柱沉降，似乎是溶解的稀土元素的主要来源。轻稀土和中稀土的垂直剖面随深度几乎呈线性增加，这是所有地方的共同特征，但其浓度水平因流域和元素而异。这表明它们的海洋分布对颗粒通量和稀土元素组成的变化有快速的响应，与Th类似，通过与悬浮颗粒和沉降颗粒的可逆交换平衡。相对重要性的垂直地球化学过程的可逆清除水平盆地规模的海洋环流与被动再生，如营养物质从轻到重的稀土系统下降。使用一个模型，在孟加拉湾的稀土元素的平均海洋停留时间估计为37年的铈140 - 1510年的严格三价稀土。在安达曼海的深水中，安达曼-尼科巴海脊（最大底床深度约为1800英寸）将其与孟加拉湾隔离开来，稀土元素浓度几乎是均匀的，这可能是由于快速的垂直混合。稀土元素（III）的含量与孟加拉湾深水中1250的含量相近，与其它海洋学特征一致。然而，深水的稀土元素组成似乎略有改变，优先清除轻稀土（111）在底部边界的盆地。(C)2002 Elsevier Science B.V.保留所有权利。
Vertical profiles of dissolved rare earth elements (REEs) were obtained in the Bay of Bengal and the Andaman Sea. The REE concentrations at various depths in the Bay of Bengal are the highest in the Indian Ocean. This is attributable ultimately to the large outflow of the Ganges-Brahmaputra and Irrawaddy rivers, but the dissolved REE flux to surface waters alone cannot explain the large and near-constant REE enrichment throughout the entire water column. The underlying fan sediments serve as not a source but a sink for dissolved REE(III)s. Absence of excess Ra-228 in the deep waters suggests that lateral input of dissolved REEs from slope sediments is also small in these regions. Partial (< 0.3%) dissolution of detrital particles, which are carried by the rivers and lateral surface currents and subsequently settle through the water column, appears to be a predominant source for the dissolved REEs. Vertical profiles showing an almost linear increase with depth are common features for the light and middle REEs everywhere, but their concentration levels are variable from basin to basin and from element to element. This suggests that their oceanic distributions respond quickly to the variation of particle flux and its REE composition through reversible exchange equilibrium with suspended and sinking particles much like the case for Th. The relative importance of the vertical geochemical processes of reversible scavenging over the horizontal basin-scale ocean circulation with passive regeneration like nutrients decreases systematically from the light to the heavy REEs. Using a model, the mean oceanic residence times of REEs in the Bay of Bengal are estimated to range from 37 years for Ce to 140-1510 years for the strictly trivalent REEs. In the deep water of the Andaman Sea, isolated from the Bay of Bengal by the Andaman-Nicobar Ridge (maximum sill depth of similar to1800 in), the REE concentrations are almost uniform presumably due to rapid vertical mixing. The REE(III) concentrations are similar to that of similar to1250 in depth water in the Bay of Bengal, consistent with other oceanographic properties. However, the REE composition of the deep water appears to be altered slightly by preferential scavenging of the light REE(111) at the bottom boundary of the basin. (C) 2002 Elsevier Science B.V. All rights reserved.