The influence of thermodynamic and kinetic factors on the formation and dissolution of calcium phosphates in complex geochemical systems

复杂地球化学系统中热力学和动力学因素对磷酸钙形成和溶解的影响

• 批准号: 283810620
• 负责人: Dr. Julian Oxmann
• 金额: --
• 依托单位: Leibniz-Zentrum für Marine Tropenforschung (ZMT)
• 依托单位国家: 德国
• 项目类别: Research Grants
• 财政年份: 2015
• 资助国家: 德国
• 起止时间: 2014-12-31 至 2020-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/283810620?language=en
• 关键词: influence; thermodynamic; kinetic; factors; formation

Formation of calcium phosphate (Ca-P) is an important process in removing phosphorus (P) from natural waters, with carbonate fluorapatite (CFAP) being a major sink for reactive P in the ocean. Local conditions may either favor direct apatite formation or nucleation of apatite precursors. In situ precipitation and dissolution of these minerals are, however, difficult to predict owing to the interplay between thermodynamic and kinetic factors. This project assesses effects of these factors on Ca-P precipitation and dissolution by combining conventional sediment and pore-water analyses, experimental approaches and geochemical modelling with state-of-the-art techniques for determining solid-phase P speciation. Main objectives are to (i) determine P speciation in Baltic Sea sediments; (ii) estimate the time of Ca-P precipitation in sea and brackish water under different experimental conditions using a nucleation assay; (iii) determine solubilities of Ca-P phases in sediment-water systems using a dissolution assay that mimics marine, brackish and freshwater conditions; (iv) identify the role of apatite precursors during P diagenesis; (v) verify results using geochemical models and cross-validate analytical methods. Techniques for determining Ca-P phases include chemical and synchrotron-based methods with accompanying scanning electron microscopy and electron microprobe analysis. These approaches will, together with the method validation, contribute to better understand P dynamics and P diagenesis in complex natural environments.

磷酸钙 (Ca-P) 的形成是从天然水中去除磷 (P) 的重要过程，而碳酸盐氟磷灰石 (CFAP) 是海洋中活性磷的主要汇。局部条件可能有利于直接形成磷灰石或有利于磷灰石前体的成核。然而，由于热力学和动力学因素之间的相互作用，这些矿物的原位沉淀和溶解很难预测。该项目通过将传统沉积物和孔隙水分析、实验方法和地球化学建模与确定固相磷形态的最先进技术相结合，评估这些因素对钙磷沉淀和溶解的影响。主要目标是 (i) 确定波罗的海沉积物中磷的形态； (ii) 使用成核测定法估计不同实验条件下海水和咸水中 Ca-P 沉淀的时间； (iii) 使用模拟海洋、咸水和淡水条件的溶解测定法确定沉积物-水系统中 Ca-P 相的溶解度； (iv) 确定磷灰石前体在磷成岩过程中的作用； (v) 使用地球化学模型和交叉验证分析方法验证结果。确定 Ca-P 相的技术包括基于化学和同步加速器的方法以及扫描电子显微镜和电子微探针分析。这些方法与方法验证一起将有助于更好地了解复杂自然环境中的磷动力学和磷成岩作用。