Osmium in seawater: vertical profiles of concentration and isotopic composition in the eastern Pacific Ocean
Osmium in seawater: vertical profiles of concentration and isotopic composition in the eastern Pacific Ocean
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DOI：
10.1016/s0012-821x(99)00233-2
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发表时间：
1999-11
影响因子：
5.3
通讯作者：
O. B. Woodhouse;G. Ravizza;K. Falkner;P. Statham;B. Peucker‐Ehrenbrink
中科院分区：
文献类型：
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作者：
O. B. Woodhouse;G. Ravizza;K. Falkner;P. Statham;B. Peucker‐Ehrenbrink
用一种新的方法测定了东太平洋海水样品的锇浓度（6.6 ~ 9.8pg/l）和同位素组成（平均~（187）Os/~（188）Os = 1.067±0.011;误差2σ）。与最近在印度洋的工作相比，测得的Os浓度显示与氧最小区的核心和光透射的局部最小值相一致的30%耗尽。虽然我们不能排除的可能性，即在海水中的抗氧化形式的Os防止同位素之间的平衡富集的同位素尖峰和自然发生的Os，这将导致测量浓度偏低的值，我们解释这些数据的证据，在这个区域的海水中的Os的非保守行为。这些数据可以用两种可能的过程来解释：从大陆坡和/或现场吸附的Os下沉颗粒上的低Os浓度的水团的水平平流。从数据中还不清楚每个过程在多大程度上对Os最小值有贡献。这些东太平洋样品的Os同位素组成是最近报道的印度洋，这表明在这两个海洋盆地的海水Os的同位素组成是难以区分的精度水平的2%。在东太平洋海隆9°46′N活跃喷口附近采集的中性浮力热液羽流样品的Os浓度和同位素组成与周围深水相似。这表明，从高温热液喷口的Os的通量是不是大的相比，在环境海水中的Os的库存。过滤和未过滤的样品之间的比较表明，在这些样品中的海水Os的大部分是在溶解相。
Os concentrations (6.6 to 9.8 pg/l) and isotopic compositions (mean187Os/188Os = 1.067±0.011; 2σ error) were measured by a new method in seawater samples collected from the eastern Pacific Ocean. In contrast to recent work in the Indian Ocean, measured Os concentrations display a 30% depletion coincident with both the core of the oxygen minimum zone, and a local minimum in light transmission. Whilst we cannot preclude the possibility that an oxidation-resistant form of Os in seawater prevented isotopic equilibration between the enriched isotope spike and naturally occurring Os, which would bias measured concentrations to low values, we interpret these data as evidence of non-conservative behaviour of Os in seawater in this zone. The data may be explained by two possible processes: the horizontal advection of a water mass of low Os concentration from the continental slope and/or the in-situ adsorption of Os onto sinking particles. To what extent each process is contributing to the Os minimum is unclear from the data. The Os isotopic composition of these Eastern Pacific samples are within 2% of those recently reported from the Indian Ocean, which indicates that the isotopic composition of seawater Os in these two ocean basins is indistinguishable at this level of precision. Neutrally buoyant hydrothermal plume samples collected in close proximity to active vents at 9°46′N on the East Pacific Rise have Os concentrations and isotopic compositions similar to ambient deep water. This shows that the flux of Os from high temperature hydrothermal vents is not large compared to the inventory of Os in ambient seawater. Comparisons between filtered and unfiltered samples show that the majority of seawater Os in these samples is in the dissolved phase.