In order to assess the potential risk of metal release from deep-sea sediments in response to pH decrease in seawater, the mobility of elements from ferromanganese (Fe–Mn) nodules and pelagic clays was examined. Two geochemical reference samples (JMn-1 and JMS-2) were reacted with the pH-controlled artificial seawater (ASW) using a CO₂-induced pH regulation system. Our experiments demonstrated that deep-sea sediments have weak buffer capacities by acid–base dissociation of surface hydroxyl groups on metal oxides/oxyhydroxides and silicate minerals. Element concentrations in the ASW were mainly controlled by elemental speciation in the solid phase and sorption–desorption reaction between the charged solid surface and ion species in the ASW. These results indicated that the release of heavy metals such as Mn, Cu, Zn and Cd should be taken into consideration when assessing the influence of ocean acidification on deep-sea environment.

中文翻译：

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海洋酸化对深海铁锰结核和浮游粘土的潜在影响：使用人工海水的改良评估

为了评估响应海水pH值降低而从深海沉积物中释放出金属的潜在风险，我们研究了锰铁（Fe-Mn）结核和浮游粘土中元素的迁移率。使用CO ₂使两个地球化学参考样品（JMn-1和JMS-2）与pH受控的人造海水（ASW）反应-诱导的pH调节系统。我们的实验表明，由于金属氧化物/羟基氧化物和硅酸盐矿物上表面羟基的酸碱解离，深海沉积物的缓冲能力较弱。ASW中的元素浓度主要由固相中的元素形态和ASW中带电的固体表面与离子种类之间的吸附-解吸反应控制。这些结果表明，在评估海洋酸化对深海环境的影响时，应考虑重金属如锰，铜，锌和镉的释放。