钒 (V) 是一种氧化还原敏感的微量金属，通常以三种氧化态（+3、+4 和 +5）之一存在于天然水中；这一特征越来越多地用于古代海洋沉积物的古氧化还原研究。然而，我们对低氧海洋环境中钒地球化学的了解仍然有限，特别是关于钒与绿锈等还原铁矿物的相互作用。碳酸盐绿锈 (GR CO3 ) 是在一些现代含铁环境中发现的混合 Fe II /Fe III 相，例如马塔诺湖（印度尼西亚），并且可能在古代含铁海洋系统中含量丰富，它们可能在自生过程中发挥了重要作用沉积物中 V 富集。在这里，我们提出了一种从海水中去除 V 的非生物途径还原并吸附到无定形GR CO3上。将新沉淀的GR CO3 (1 g L -1 )的悬浮液添加到缺氧合成海水溶液中的钒酸盐(1 mg V V L -1初始浓度)中。GR CO3除钒快速高效，20 秒内即可去除 92-99% 的 V。基于同步加速器的 X 射线吸收近边结构 (XANES) 光谱表明， GR CO3吸附的V V部分还原为 V V和 V IV的混合物，随着溶液 pH 值的增加（7.5 至 8.5），吸附 V 的平均氧化态增加（+4.3 至 +4.7）。扩展X射线吸收精细结构（EXAFS）模型表明V可能与GR CO3形成了单齿和双齿共角表面配合物的组合。随后暴露于曝气海水中，含 V 的 GR CO3在 24 小时内氧化为纤铁矿 [γ–FeO(OH)]，同时所有固相 V V 还原为V IV。在氧化过程中，V 不会释放回溶液中；相反，EXAFS 模型表明 V IV作为八面体氧钒 (VO 2+）。我们的工作进一步限制了 V 的水地球化学，这对于理解现代和古代海洋系统中 V 的循环和去除机制具有重要意义。
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Reductive sorption of vanadium by green rust in seawater
Vanadium (V) is a redox-sensitive trace metal that typically exists in one of three oxidation states (+3, +4 and +5) in natural waters; a feature increasingly used in paleoredox studies of ancient marine sediments. However, our knowledge of V geochemistry in low-oxygen marine environments is still limited, especially regarding interactions of V with reduced iron minerals such as green rust. Carbonate green rusts (GRCO3) are mixed FeII/FeIII-phases found in some modern ferruginous settings, such as Lake Matano (Indonesia), and were likely abundant in ancient ferruginous marine systems where they may have played an essential role in authigenic V enrichments in sediments. Here, we present an abiotic pathway of V removal from seawater via reduction and adsorption onto amorphous GRCO3. Suspensions of the freshly precipitated GRCO3 (1 g L−1) were added to vanadate (1 mg VV L−1 initial concentration) in anoxic synthetic seawater solutions. Vanadium removal by GRCO3 was rapid and efficient, with 92–99% of V removed in under 20 seconds. Synchrotron-based X-ray absorption near edge structure (XANES) spectroscopy showed that VV adsorbed by GRCO3 was partially reduced to a mixture of VV and VIV, with the average oxidation state of adsorbed V increasing (+4.3 to +4.7) with increasing solution pH (7.5 to 8.5). Extended X-ray absorption fine structure (EXAFS) modelling indicated that V may have formed a combination of monodentate and bidentate corner-sharing surface complexes with GRCO3. Upon subsequent exposure to aerated seawater, V-bearing GRCO3 oxidized to lepidocrocite [γ–FeO(OH)] within 24 hours, with concomitant reduction of all solid-phase VV to VIV. During oxidation, V was not released back into solution; rather, EXAFS modelling indicated that VIV was incorporated into the lepidocrocite structure as octahedral vanadyl (VO2+). Our work further constrains the aqueous geochemistry of V, which has implications for understanding V cycling and removal mechanisms in both modern and ancient marine systems.