Trace metal-Organic matter interactions in seawater: Exploring the impact of seawater chemistry on trace metal speciation in a warming and acidifying ocean.

痕量金属（TM），定义为小于1 mg kg-1，是微生物生长的重要必需营养素（Fe，Mn，Co，Cu，Ni，Zn），或在海水中浓度升高时具有毒性（Cu，Pb，Cd）。海洋目前正在经历脱氧、酸化、分层和变暖，导致依赖于物理化学条件（例如pH值、温度和盐度）的TM化学形态发生变化。虽然溶解和颗粒金属的知识提供了总库存的信息，并允许确定的重要来源的TM的海洋环境，化学形态的知识是必不可少的了解TM的生物地球化学和生物利用度或毒性。例如，以前的工作表明，无机铁在含氧海水中的溶解度很差，但溶解的铁浓度高于预期，因为有机物的络合作用。然而，目前对TM形态的了解是在实验室条件下（例如，pH=8.0，在NBS尺度上）对特定样品进行观察的，因此缺乏与海水固有物理化学性质及其对金属与有机物结合的影响的机械联系。在这里，我开发新的分析和建模工具，并利用金属树脂/有机物的相互作用，以准确地确定TM形态的ICP-MS在很宽的pH值范围内。我结合联合收割机这些测量与离子配对有机物（NICA-Donnan）模型开发的相互作用的机械描述，从而提高我们的理解，例如pH值，温度和离子强度对海洋TM循环的作用。一旦实现这种方法，它将使我们能够同时确定TM形态的多种金属的第一次，包括那些经常调查之前和TM最近的证据从同位素丰度点的重要作用，结合有机物。导出的热力学常数也将被纳入区域地球化学模式，以获得在未来的海洋情景下的TM地球化学循环在机械水平上的预测。

Trace metals (TMs), defined as less than 1 mg kg-1, are either important essential nutrients (Fe, Mn, Co, Cu, Ni, Zn) for microbial growth, or toxic (Cu, Pb, Cd) at elevated concentrations in seawater. The Ocean is currently experiencing deoxygenation, acidification, stratification and warming, resulting in changes in chemical speciation of TMs that are dependent on the physico-chemical conditions (e.g. pH, temperature and salinity). Whilst knowledge of dissolved and particulate metals provides information on total inventories and allows for identification of important sources of TMs to the marine environment, knowledge of chemical speciation is essential for understanding the biogeochemistry and bioavailability or toxicity of TMs. For example, previous work shows that inorganic Fe has a poor solubility in oxygenated seawater, but dissolved Fe concentrations are higher than expected because of complexation by organic matter. However current knowledge of TMs speciation is observed for a specific sample at laboratory conditions (e.g. pH=8.0, on the NBS scale), and therefore lack a mechanistic link to the intrinsic physico-chemical properties of seawater and their influence on metal binding to organic matter. Here I develop novel analytical and modelling tools, and utilize metal-resin/organic matter interactions to accurately determine TM speciation by ICP-MS over a wide range of pH values. I combine these measurements with an ion paring-organic matter (NICA-Donnan) model to develop a mechanistic description of the interactions and thereby improve our understanding of the roles of e.g. pH, temperature and ionic strength on marine TM cycling. Once this methodology is achieved, it will allow us to simultaneously determine TM speciation for multiple metals for the first time, including those frequently investigated before and TMs where recent evidence from isotope abundance points to an important role for binding to organic matter. The derived thermodynamic constants will also be incorporated into regional biogeochemical models, in order to obtain predictions of TM biogeochemical cycling at a mechanistic level under future ocean scenarios.