Hydrothermal vents: A previously unrecognized source of actinium-227 to the deep ocean
Hydrothermal vents: A previously unrecognized source of actinium-227 to the deep ocean
复制标题
热液喷口：以前未被认识的深海锕227来源
DOI：
10.1016/j.marchem.2015.09.002
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发表时间：
2015
期刊：
影响因子：
3
通讯作者：
W. Moore
中科院分区：
文献类型：
--
作者：
L. Kipp;M. Charette;D. Hammond;W. Moore
锕-227（t1/2= 21.77 y）是由钚-231（t1/2= 32，760 y）衰变产生的。深海沉积物富含231 Pa，因此为深海提供了更易溶解的227 Ac来源，在深海，它可用作深海底辟混合的示踪剂。在这项研究中，我们研究了在美国GEOTRACES北大西洋断面（2011年）期间收集的覆盖TAG喷口场（26.14°N，44.83°W，大西洋中脊）的中性浮力热液羽流中溶解和颗粒227 Ac的分布。羽流中微粒和溶解227 Ac的活动都很高，这表明热液喷口可能是海洋环境中这种同位素的一个以前未被认识的来源。我们认为，喷口流体是227 Ac富集的主要来源。根据羽流中溶解和颗粒状227 Ac的活度，使用3 He稀释模型得出热液227 Ac端元活度为1.5 × 104-2.5 × 104 dpm m− 3。假设TAG是中大西洋海岭沿着所有喷口的特征，那么进入大西洋深部的~（227）Ac的热液来源估计为来自大西洋沉积物的通量的1.9-5.8%。虽然这种热液通量可能不会对227 Ac的海洋总量产生很大影响，但在使用这种同位素作为热液活动存在的地区深海混合的示踪剂时，必须考虑到这一点。
Actinium-227 (t1/2= 21.77 y) is produced by decay of protactinium-231 (t1/2= 32,760 y). Abyssal sediments are enriched in231Pa and thus provide a source of the more soluble227Ac to the deep-sea, where it can be used as a tracer of deep ocean diapycnal mixing. In this study, we examine the distribution of dissolved and particulate227Ac within a neutrally buoyant hydrothermal plume overlying the TAG vent field (26.14°N, 44.83°W, Mid-Atlantic Ridge) collected during the U.S. GEOTRACES North Atlantic Transect (2011). Elevated activities of both particulate and dissolved227Ac within the plume indicate that hydrothermal vents may be a previously unrecognized source of this isotope to the marine environment. We contend that vent fluids are the main source of the227Ac enrichment. Based on the activities of dissolved and particulate227Ac within the plume, a3He dilution model was used to derive a hydrothermal227Ac end-member activity of 1.5 × 104–2.5 × 104dpm m− 3. Assuming that TAG is characteristic of all vents along the Mid-Atlantic Ridge, the hydrothermal source of227Ac to the deep Atlantic is estimated to be 1.9–5.8% of the flux from Atlantic sediments. Although this hydrothermal flux may not have a large impact on the total oceanic inventory of227Ac, it must be considered when using this isotope as a tracer of deep ocean mixing in areas where hydrothermal activity is present.