硅藻生物的典型必需金属元素在其壳体中的赋存对硅藻蛋白石结构和表面性质的影响机理

Fe, Ca and Mn are the biologically essential metal elements of diatoms. Many researches have demonstrated that diatoms are obtaining these elements during their life. However, very few researches focus on the occurrence of these elements in the structure of inorganic frustules of diatoms (diatomaceous opal). Based on our previous study, it is a very definite possibility of existence of these elements in the structure of the diatom shells. Occurrence of these elements have significant effects on the structure and surface property of diatomaceous opal. . In this study, the original diatoms are selected to be cultured and their diatom shells (diatomaceous opal) with/without additive Fe, Ca or Mn will be collected. Several diatomaceous opal samples are to be obtained by purification of diatomaceous earth. Comparative analysis will be selected to study the above mentioned diatomaceous opal samples. The occurrence characteristics, including content, distribution and chemical valence of structural Fe, Ca and Mn will be investigated and their influence mechanism on the microstructure and surface property of diatomaceous opal will be explored by combining spectrometric measurement and electron microscopy analysis with high-resolution. Further researches will be performed to understand the geochemical properties of diatomaceous opal, such as solubility. The results will be in favor of the further understanding of the mineral characters and geochemical behavior of diatomaceous opal, and provide the key theory and experimental basis for driving mechanism of diatomaceous opal’s formation process on geochemical cycle of Fe, Ca and Mn. Consequently, the study shows significant research meanings.

铁、钙、锰等元素是硅藻生命周期的必需金属元素。大量研究已经证实硅藻生物在生长过程中会获取这些元素，但很少有研究关注其是否进入到硅藻的无机壳体（即硅藻蛋白石）结构中。申请者前期工作结果说明，上述元素很有可能进入硅藻蛋白石结构之中，并可能对其矿物结构和表面性质产生重要影响。. 本项目拟针对源自活体硅藻的硅藻蛋白石和源自硅藻土矿样的硅藻蛋白石开展对比研究，采用高分辨矿物谱学、微区分析等方法，深入探索铁、钙、锰等金属元素在硅藻蛋白石中的赋存特征（赋存量、分布特征、价态等），掌握其赋存对硅藻蛋白石微结构和表面性质的影响和相关机理，进而探讨相关影响对硅藻蛋白石的溶解性等地球化学特性的制约机制。所获成果将显著提升对硅藻蛋白石矿物结构和表面性质及其地球化学行为的认识，为理解硅藻蛋白石形成过程对铁、钙、锰、硅等元素地球化学循环的驱动机制提供理论和实验依据。因此，具有重要的研究意义。

硅藻蛋白石源于硅藻的壳体，是硅藻土矿床的主要矿物。长期以来，硅藻蛋白石被认为是“纯相二氧化硅”。然而，大量研究已经证实硅藻生物在生长过程中会获取部分金属元素，这些元素很有可能会进入硅藻蛋白石骨架并赋存，并可能对其矿物结构和表面性质产生重要影响。但相关研究尚未开展，因此，对硅藻蛋白石存在认知“盲区”。. 针对上述问题，本项目以实验室富金属离子环境下培养所获硅藻蛋白石和天然（硅藻土矿床和沉积物中的）硅藻蛋白石为研究对象，开展对比研究，对硅藻蛋白石的结构和表面性质以及金属元素赋存所产生的效应等有了新的认知。主要的成果如下：（1）通过生物-元素界面反应性研究，发现了硅藻蛋白石结构中赋存有铝等金属元素，修正了长期以来对硅藻蛋白石是“纯相二氧化硅矿物”的误判；（2）发现硅藻土中的硅藻蛋白石表面具有纳米铝铁质氧化物膜，重塑了对硅藻土矿石性质的认知；（3）发现湖泊硅藻蛋白石是地球的重要铝“汇”，揭示了湖相环境中以硅藻蛋白石为介质的碳-硅-铝共循环机制及其生物地球化学效应；（4）基于硅藻-粘土矿物的界面反应机制，提出了提高硅藻固碳效率的方法并阐释了其机制，以此为依据提出了“矿物增效生物泵（MeBP）”的假说。