A multi-modal approach to measuring particulate iron speciation in buoyant hydrothermal plumes
A multi-modal approach to measuring particulate iron speciation in buoyant hydrothermal plumes
复制标题
测量浮力热液羽流中颗粒铁形态的多模式方法
DOI：
10.1016/j.chemgeo.2020.120018
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发表时间：
2021
期刊：
影响因子：
3.9
通讯作者：
Toner, Brandy M.
中科院分区：
文献类型：
--
作者：
Stewart, Brandy D.;Sorensen, Jeffry V.;Wendt, Kathleen;Sylvan, Jason B.;German, Christopher R.;Anantharaman, Karthik;Dick, Gregory J.;Breier, John A.;Toner, Brandy M.
在浮力热液羽流中活跃的过程预计会调节铁等元素向深海的流动;然而，尚有待通过观测或模型对其进行全面描述。在这项研究中，我们比较观察到的颗粒Fe（pFe）形态与热力学（平衡）反应路径建模三个喷口领域在东部刘扩散中心（ELSC）。在每个地点，使用遥控潜水器进行现场过滤，从热液羽流的浮力上升部分收集颗粒。通过同步加速器微探针X射线荧光成像（XRF），X射线衍射（XRD），XRF光谱，和X射线吸收近边结构（XANES）光谱在Fe 1 s边缘，以及基于XRF的化学形态映射Fe的过滤器结合的颗粒进行了分析。对于ELSC的浮力羽流，固态化学的多样性很高，结晶不良，亚稳定相很常见。我们证明，要充分描述的结晶到非晶字符羽pFe，一个多模态XRD-XANES分析方法是必要的。我们发现，平衡建模方法工作良好的黄铁矿，但表现不佳的重要家庭的亚稳pFe，即铁（oxyhydr）氧化物和单硫化物。根据我们的研究结果，我们建议未来的实地考察战略性地探索代表不同地点特定条件的地点，以更好地捕捉羽流中活跃的全方位过程。我们还建议发展动力学模型，以及扩大热力学数据库，以更好地反映羽流的固态成分。这些步骤应使海洋学家了解控制铁形态的羽流足够好，以创建现实的热液通量的海洋模型的过程。
Processes active within buoyant hydrothermal plumes are expected to modulate the flux of elements, such as Fe, to the deep ocean; however, they are yet to be described in a comprehensive manner through observations or models. In this study, we compare observed particulate Fe (pFe) speciation with thermodynamic (equilibrium) reaction path modeling for three vent fields in the Eastern Lau Spreading Center (ELSC). At each site, particles were collected from the buoyant rising portion of hydrothermal plumes using in situ filtration with a Remotely Operated Vehicle. Filter bound particles were analyzed by synchrotron micro-probe X-ray fluorescence mapping (XRF), X-ray diffraction (XRD), XRF spectroscopy, and X-ray absorption near edge structure (XANES) spectroscopy at the Fe 1 s edge, as well as XRF-based chemical speciation mapping for Fe. For buoyant plumes of the ELSC, diversity in solid-state chemistry was high, and poorly crystalline, meta-stable phases were common. We demonstrate that to fully describe the crystalline-to-noncrystalline character of plume pFe, a multi-modal XRD-XANES analytical approach is needed. We found that an equilibrium modeling approach worked well for pyrite but performed poorly for important families of meta-stable pFe, namely Fe (oxyhydr)oxides and monosulfides. Based on our findings, we recommend future field expeditions strategically explore sites representing a diversity of site-specific conditions to better capture the full range of processes active in plumes. We also recommend development of kinetic models, as well as expansion of thermodynamic databases to better reflect the solid-state composition of plumes. These steps should allow oceanographers to understand the processes controlling Fe speciation in plumes well enough to create realistic models of hydrothermal fluxes to the ocean.
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