Collaborative Research: Silicate Reactions Kinetics in a Major Groundwater Aquifer

合作研究：主要地下水含水层中的硅酸盐反应动力学

• 批准号: 0423971
• 负责人: Chen Zhu
• 金额: $ 3.59万
• 依托单位: Indiana University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-02-15 至 2005-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0423971&HistoricalAwards=false
• 关键词: Collaborative; Research; Silicate; Reactions; Kinetics

0003816 ZhuWeathering rates for silicate minerals exert important controls on groundwater and surface water quality, nutrient availability, and the global carbon cycling and its impact on global climatic changes over geological time. Yet, weathering rates derived from watersheds and soil profiles are several others of magnitude slower than laboratory measurements. Understanding this large discrepancy remains a fundamental problem in modern geochemistry, hampering our ability to understand and predict surficial processes and environmental changes quantitatively.To provide insights into discrepancy, we propose to study the in situ silicate dissolution and precipitation rates in large aquifer system with relatively simple and well-constrained chemistry and hydrology. The chosen field site is a sandstone aquifer, located in northern Arizona and mostly composed of the Navajo sandstone. Groundwater in this aquifer has an optimal residence time up to approximately 35,000 years. The kinetic rate constants derived from this aquifer first will be much better constrained than in watersheds and soil profiles because of the saturated hydrologic environment and unusually abundant data. A new transmission electron microscope at John Hopkins, with capabilities 0.12nm imaging and 1 nm compositional mapping resolution, will provide atomic scale information of microstructure and fine-scale chemical variations at weather feldspar.

随着地质时间的推移，硅酸盐矿物的风化速率对地下水和地表水的质量、养分有效性、全球碳循环及其对全球气候变化的影响具有重要的控制作用。然而，从流域和土壤剖面得出的风化速率比实验室测量结果要慢几个数量级。理解这种巨大的差异仍然是现代地球化学的一个基本问题，它阻碍了我们定量地理解和预测地表过程和环境变化的能力。为了提供对差异的见解，我们建议在相对简单且化学和水文约束良好的大型含水层系统中研究原位硅酸盐溶解和降水速率。选定的场地是一个砂岩含水层，位于亚利桑那州北部，主要由纳瓦霍砂岩组成。该含水层中的地下水的最佳停留时间约为35000年。由于饱和的水文环境和异常丰富的数据，首先从该含水层得到的动力学速率常数将比在流域和土壤剖面中得到的约束要好得多。约翰霍普金斯大学的一种新型透射电子显微镜，具有0.12纳米成像能力和1纳米成分测绘分辨率，将提供天气长石微观结构和精细尺度化学变化的原子尺度信息。