Collaborative Research: A New Paradigm for Imperfectly-Mixed Chemical Reactions

许多在液体中移动的化学物质会发生反应。 这些反应通常将有毒化合物转化为无害的副产品。一个例子是清理泄漏到地下蓄水层的汽油。 这是非常困难的，使用目前的模型，以预测反应的持续时间或速度，主要是因为不良的混合反应物。这定义了一个重要的理论和实践问题，因为目前大多数水文系统中的反应性输运模型都是基于对经典定律的经验调整，而经典定律是建立在有缺陷的混合假设基础上的。为了在这些系统中进行可靠的预测，新的和改进的方法对于科学家和工程师，以及最终在环境污染和修复等领域工作的决策者，利益相关者和政策制定者至关重要。 然而，混合限制反应的问题远远超出了激发这一提议的水文学例子。最近的研究表明，混合限制反应在地球范围内的系统中起着主导作用，包括大气中的反应（例如，臭氧生成），饮用水含水层（例如，污染物的修复），在地质盆地中（例如，石油生成），以及岩浆、热液区和矿体。 该项目将应用于许多领域，包括与气候变化相关的大气反应，生态和微生物化学系统。研究人员已经开发出新的计算机模型，证明需要新的范例来模拟非线性混合系统中的反应。 首先，该项目将应用“时间从属”的理论方法，该方法将随机粒子迁移时间计算到活性反应位点。 从属已经成功地应用于简单的系统，但它仍然有待证明，它可以扩展到更复杂的反应，几何形状和流动模式。 第二，该项目将开发一种跟踪浓度扰动增长的随机连续方法。这些干扰包括低浓度区，这是降低反应速率的关键。第三，该项目将建立在新的计算机模型，证明是正确的，为基准的理论结果和促进大规模的反应模拟的目的。 所有的方法都将通过详细的数学分析和应用于研究良好的实验室和现场实验来统一。

Many of the chemicals that move within fluid undergo reactions. Often the reactions convert toxic compounds into harmless by-products. An example is the cleanup of gasoline that has leaked into a groundwater aquifer. It is very difficult, using current models, to predict the duration or rate of the reactions, primarily because of poor mixing of the reactants. This defines a significant theoretical and practical problem, because most current models of reactive transport in hydrologic systems are based on empirical adjustments to classical laws, which are built upon the flawed well-mixed assumption. In order to make reliable predictions in such systems, novel and improved methods are critical for the scientists and engineers, and ultimately decision makers, stakeholders, and policy developers working in fields such environmental contamination and remediation. However, the problem of mixing-limited reaction goes far beyond the hydrologic examples that motivated this proposal. Recent studies show that mixing-limited reactions play a dominant role in Earth-bound systems across a huge range of scales, including reactions in the atmosphere (e.g., ozone creation), in drinking-water aquifers (e.g., remediation of contaminants), in geologic basins (e.g., petroleum generation), and in magmas, hydrothermal areas, and ore bodies. This project will have application to many fields, including climate-change related atmospheric reactions, ecologic, and micro-biochemical systems. The investigators have developed new computer models that demonstrate the need for new paradigms of simulating reactions in imperfectly-mixed systems. First, the project will apply the theoretical approach of "time subordination" that accounts for random particle migration time to active reaction sites. Subordination has been successfully applied to simple systems, but it remains to be proven that it can be extended to more complicated reactions, geometries, and flow patterns. Second, the project will develop a random continuum method that tracks the growth of concentration disturbances. These disturbances include low concentration zones that are the key to slower reaction rates. Third, the project will build on the new computer models, shown to be correct, for the purpose of benchmarking theoretical results and facilitating large-scale reactive simulations. All approaches will be unified through detailed mathematical analysis and application to well-studied laboratory and field experiments.