Particle-Seawater Interaction of Neodymium in the North Atlantic
Particle-Seawater Interaction of Neodymium in the North Atlantic
复制标题
北大西洋钕的粒子与海水相互作用
DOI：
10.1021/acsearthspacechem.0c00034
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发表时间：
2020
影响因子：
3.4
通讯作者：
Stichel T
中科院分区：
文献类型：
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作者：
Stichel T
在古海洋学中，溶解钕(ε-ND)作为水团示踪剂得到了广泛的应用。然而，现代ND生物地球化学循环的一个方面很少被研究，那就是海水中溶解相和颗粒相之间的相互作用。我们在这里介绍了北大西洋西部沿GEOTRACES GA02样带的五个站的颗粒ND同位素组成(εNdp)和浓度([ND]p)的第一个区域数据集，以及以前公布的溶解ND同位素组成(εNdd)和浓度([ND]d)1。来自我们新的颗粒数据集的主要观测和解释包括：(1)[ND]Ptt对单位体积海水的总ND库存量(∼5%)的低比例贡献，海底边界层中的显著增加高达45%。(2)随着水深的增加，悬浮颗粒物([ND]SPM)和成岩物质组分中的ND浓度增加，表明贫ND相被去除。(3)亚极和副热带环流中颗粒物的不同来源，从拉布拉多盆地(旧大陆地壳)附近的εNDP≈−20、冰岛和格陵兰之间的εNDP≈−4(年轻的镁铁源)到亚热带εNDP≈−13的值(类似于非洲尘埃信号)证明了这一点。(4)亚极涡旋εNdpA的垂直非均质性以及与周围海水的较大偏离表明本区有造岩颗粒的平流。(5)副热带环流中垂直均匀的εNdp值与εNdd值难以区分，表明垂直颗粒物供应占优势。可逆清除过程似乎只影响3公里以下的颗粒物特征。总体而言，我们没有发现粒子溶解增强的证据，这通常被用来解释在北大西洋观察到的溶解ND的增加。
Dissolved neodymium (Nd) isotopes (expressed as εNd) have been widely used as a water mass tracer in paleoceanography. However, one aspect of the modern biogeochemical cycle of Nd that has been sparsely investigated is the interplay between dissolved and particulate phases in seawater. We here present the first regional data set on particulate Nd isotope compositions (εNdp) and concentrations ([Nd]p) from five stations in the western North Atlantic Ocean along the GEOTRACES GA02 transect, in conjunction with previously published dissolved Nd isotope compositions (εNdd) and concentrations ([Nd]d)1. Key observations and interpretations from our new particulate data set include the following: (1) Low fractional contributions of [Nd]pto the total Nd inventory per volume unit of seawater (∼5%), with significant increases of up to 45% in benthic boundary layers. (2) Increasing Nd concentrations in suspended particulate matter ([Nd]SPM) and fractions of lithogenic material with water depth, suggesting the removal of Nd poor phases. (3) Different provenances of particulates in the subpolar and subtropical gyres as evidenced by their Nd isotope fingerprints reaching from εNdp≈ −20 near the Labrador Basin (old continental crust), over εNdp≈ −4 between Iceland and Greenland (young mafic provenance), to values of εNdp≈ −13 in the subtropics (similar to African dust signal). (4) Vertical heterogeneity of εNdpas well as large deviations from ambient seawater values in the subpolar gyre indicate advection of lithogenic particles in this area. (5) Vertically homogeneous εNdpvalues in the subtropical gyre, indistinguishable from εNddvalues, are indicative of predominance of vertical particulate supply. The process of reversible scavenging only seems to influence particulate signatures below 3 km. Overall, we do not find evidence on enhanced particle dissolution, often invoked to explain the observed increase in dissolved Nd in the North Atlantic.