Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), School of Energy and Environment, State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong, China; Research Centre for the Oceans and Human Health, City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, China.
Hong Kong Branch of the Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), School of Energy and Environment, State Key Laboratory of Marine Pollution, City University of Hong Kong, Kowloon, Hong Kong, China; Research Centre for the Oceans and Human Health, City University of Hong Kong Shenzhen Research Institute, Shenzhen 518057, China; Southern Marine Science and Engineering Guangdong Laboratory (Guangzhou), Guangzhou 511458, China.
Sci Total Environ. 2021 Jun 1;771:145367. doi: 10.1016/j.scitotenv.2021.145367. Epub 2021 Jan 23.
Determining the size speciation and chemical transformation of trace metals is of paramount in order to better assess the impact of hydrothermal activities on the ocean metal budgets. In this study, we examined the concentration and size speciation of dissolved trace metals (i.e. Mn, Fe, Cu, Ni, Mo, As, Pb, Cd) in the hydrothermal plumes of two vent fields (i.e. Longqi and Tiancheng) on the Southwest Indian Ridge. The majority of dissolved Mn (75-100%) in the buoyant and non-buoyant plumes were presented as soluble Mn (<1 kDa), while dissolved Fe in the buoyant plume contained considerable colloidal Fe (54-95%). More than 66% of hydrothermally dissolved Fe was removed in the buoyant plume within a short distance of dispersion. Except for the samples most proximal to the fluid source, concentrations of Cu, Ni and Mo in the plumes were comparable to those of the background seawater and independent of the plume dilution. Concentrations of dissolved As and Pb in the buoyant plume of the Tiancheng field were higher than those of the Longqi field, resulting from the scavenging of As in the Longqi field and the release of Pb from metal sulfide dissolution in the Tiancheng field. Concentrations of dissolved Cd in the non-buoyant plume were nearly identical to the background seawater and soluble Cd was dominant (75-92%) in the soluble phase. In contrast, 33-96% (or 0.024-0.085 μg/kg) of dissolved Cd was removed in the buoyant plume and the remaining dissolved Cd was mainly in colloidal phase (up to 96%), suggesting that hydrothermal plume was likely an important sink of oceanic Cd and colloidal ligands played an important role in the stabilization of hydrothermal Cd. Our study has demonstrated the very dynamic nature of trace metal speciation in hydrothermal vent fluids.
为了更好地评估热液活动对海洋金属收支的影响，确定痕量金属的大小形态和化学转化至关重要。在这项研究中，我们研究了西南印度洋中脊两个喷口场（即龙崎和天成）热液羽流中溶解痕量金属（即 Mn、Fe、Cu、Ni、Mo、As、Pb、Cd）的浓度和形态。在浮力和非浮力羽流中，大部分溶解的 Mn（75-100%）呈可溶性 Mn（<1 kDa）形式存在，而浮力羽流中的溶解 Fe 含有相当数量的胶体 Fe（54-95%）。在短距离的扩散过程中，超过 66%的水热溶解 Fe 被浮力羽流去除。除了最靠近流体源的样品外，羽流中 Cu、Ni 和 Mo 的浓度与背景海水相当，且不受羽流稀释的影响。天成场浮力羽流中溶解的 As 和 Pb 浓度高于龙崎场，这是由于龙崎场的 As 被清除以及天成场的金属硫化物溶解释放 Pb。非浮力羽流中溶解的 Cd 浓度与背景海水几乎相同，且可溶相中可溶性 Cd 占主导地位（75-92%）。相比之下，在浮力羽流中，有 33-96%（或 0.024-0.085μg/kg）的溶解 Cd 被去除，剩余的溶解 Cd 主要以胶体相存在（高达 96%），这表明热液羽流可能是海洋 Cd 的一个重要汇，胶体配体在稳定水热 Cd 方面发挥了重要作用。本研究表明了热液喷口流体中痕量金属形态非常动态的本质。
