The Kinetics of Silica Dissolution: An Integrated Experimental Investigation of Quartz and Amorphous Silica Reactivity in the Mixed Solute Compositions of Natural Waters

9903349鸽子的溶解动力学的两个最丰富的二氧化硅多晶型物，石英和无定形二氧化硅，有重要的控制二氧化硅分区内的主要水库地球环境。 这些系统中的液体通常含有大量的主要溶质，钠、钾、钙和镁。 这些阳离子大大提高了SiO2的溶解速率超过那些在纯（去离子）水中测量。 相比之下，微摩尔水平的铝表现出相反的速率抑制二氧化硅溶解在近中性到弱酸性pH值。定量和机械的理解率介导的影响是必不可少的预测二氧化硅流动性的数值模型的准确性。 这项研究将回答一个一阶问题：溶解的成分如何作为一种溶质混合物，在自然环境的复杂流体中控制二氧化硅溶解的净速率？利用整合地球化学动力学和表面科学技术的实验方法，这项研究将量化石英和无定形二氧化硅的溶解速率，（30-300 ℃）在精心设计的溶液中，该溶液含有作为单一盐的溶质和作为浓度和pH值的函数的混合物。说明二氧化硅浓度。 将使用原位原子力显微镜、表面滴定和非原位XPS和俄歇分析对选定的二氧化硅表面进行平行调查。 这些发现将使我们能够构建一个定量模型，了解溶质如何控制开始接近真实世界流体的溶液中结晶和无定形二氧化硅的反应性。

9903349DoveThe dissolution kinetics of the two most abundant SiO2 polymorphs, quartz and amorphous silica, have important controls on silica partitioning within major reservoirs of Earth environments. Fluids throughout these systems typically contain significant concentrations of the major solutes, sodium, potassium, calcium and magnesium. These cations greatly enhance SiO2 dissolution rates over those measured in pure (deionized) water. In contrast, micromolar levels of aluminum exhibit an opposing rate-inhibition of silica dissolution at near-neutral to weakly-acidic pH. A quantitative and mechanistic understanding of rate-mediating effects is essential to the accuracy of numerical models which predict silica mobility. This study will answer a first order question: How do dissolved constituents act in concert as a solute mixture to control net rates of silica dissolution in the complex fluids of natural environments? Using an experimental approach that integrates techniques from geochemical kinetics and surface science, this study will quantify rates of quartz and amorphous silica dissolution (30-300 degrees C) in carefully designed solutions that contain solutes as single salts and mixtures as a function of concentration and pH. Rates will be determined using our hydrothermal mixed flow reactor system over a range of reaction affinity by adjusting steady state silica concentrations. Parallel investigations of selected silica surfaces will be conducted using in situ Atomic Force Microscopy, surface titrations, and ex situ XPS and Auger analyses. The findings will allow us to construct a quantitative model for how solutes control the reactivity of crystalline and amorphous silica in solutions that begin to approximate real-world fluids.