A NEW APPROACH TO EXPERIMENTAL DETERMINATION OF COUPLED SILICATE DISSOLUTION - PRECIPITATION REACTION RATES AT AMBIENT CONDITIONS WITH SI ISOTOPE SPIKES

许多社会紧迫的环境问题和问题，如全球变暖和缓解它的策略，以及对地球临界带的压力——地壳上薄薄的一层，从植被冠层到土壤和地下水，维持着人类的生活，是地球上大多数陆地生物茁壮成长的地方——都与长石的溶解速度有关。长石是地壳中最丰富的矿物质，占地壳体积的50%以上。对于前者，一种减缓全球变暖的策略是地质碳封存，为此，二氧化碳被储存在地下深处的地质构造中。但注入的CO2会使储层原生盐水酸化，溶解储层中的长石，影响储层质量和长期安全储存。对于后者，长石作为临界带中丰富的矿物，其风化作用对土壤发育速率和临界带对应力的缓冲能力至关重要。然而，为了评估长石溶解或风化发生的速度（化学动力学），我们需要解决地球化学中的一个基本挑战。人们早就知道，实验室测量的长石溶解速率比实地研究估计的速率快2到5个数量级。不解决这个看似棘手的障碍，我们就不能定量地评价诸如上述的一些环境和地质过程。本研究旨在测试一个有希望的假设，该假设将部分解决明显的差异：现场和实验室速率之间的很大一部分差异是由于现场系统中溶解和沉淀反应的耦合造成的，而这在大多数实验室实验中是不存在的。历史上，在实验室环境温度下测定非常缓慢的长石溶解速率一直存在问题。反应速率慢意味着溶质可能低于分析检测限，从而影响实验的准确性。在这里，研究人员提出了一种创新的利用新开发的技术-高分辨率多收集器电感耦合等离子体质谱法-并使用一种新型的稳定硅同位素“尖峰”设计来克服这些障碍，以便在环境和接近平衡条件下确定长石反应速率，这在以前是不可能的。这项工作将涉及印第安纳大学的研究人员与他在以色列内盖夫本-古里安大学和加拿大特伦特大学的同事之间的合作。只要求为美国组织提供资金。这项研究将加强国际和多学科合作，并有助于培养一名博士后和一名来自以色列的交换生。该研究员目前正在挪威进行工业规模的二氧化碳储存项目（Sleipner项目）的研究，并将把这项研究的结果传达给二氧化碳储存社区和关键区域研究社区。

Many of society's urgent environmental concerns and problems, such as global warming and strategies that mitigate it, and the stresses on the Earth's Critical Zone - the thin veneer on the Earth's Crust from vegetation canopy to the soil and groundwater which sustains human life and is where most terrestrial life thrives on Earth - have something to do with the rates of feldspar dissolution. Feldspars are the most abundant minerals in the Earth's crust, comprising of more than 50% of the Crust volume. For the former, one global warming mitigation strategy is geological carbon sequestration, for which CO2 is stored in deep underground geological formations. However, the injected CO2 will acidify the native brine and dissolve feldspars in the reservoirs, which could affect the reservoir quality and the long-term safety of storage. For the latter, the weathering of feldspars as an abundant mineral in the Critical Zone is critical to rates of soil development and the buffer capacity of the Critical Zone to stresses. However, to assess how fast feldspar dissolution or weathering takes place (chemical kinetics), we need to wrestle with one of the fundamental challenges in geochemistry. It has been known for a long time that the laboratory measured dissolution rates of feldspars are two to five orders of magnitude faster than rates estimated from field studies. Without resolving this seemingly intractable obstacle, we cannot quantitatively evaluate a number of environmental and geological processes, such as those mentioned above. This study is designed to test the promising hypothesis that would partly resolve the apparent discrepancy: A large part of the discrepancy between in situ field and laboratory rates results from the coupling of the dissolution and precipitation reaction in the field systems which is absent in most laboratory experiments. Historically, the determination of very slow feldspar dissolution rates in laboratory at ambient temperatures has been problematic. Slow reaction rates mean that solutes may be below analytical detection limits, thus affecting the accuracy of the experiments. Here, the investigator proposes an innovative utilization of newly developed technology - High-Resolution Multi-Collector Inductively-Coupled Plasma Mass Spectrometry - and uses a novel design of stable silicon isotope 'spikes' to overcome these obstacles in order to determine feldspar reaction rates at ambient and near equilibrium conditions, not previously possible. The work will involve cooperation among the investigator at Indiana University and his colleagues at Ben-Gurion University of the Negev in Israel, and at Trent University in Canada. Funding is requested only for the US organization. This study will enhance international and multi-disciplinary collaboration and contribute to the training of a post-doctoral associate and an exchange student from Israel. Te investigator is currently conducting research on the industrial scale CO2 storage project in Norway (the Sleipner project) and will communicate the results from this study to the CO2 storage community and the Critical Zone research community.