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

许多在液体中运动的化学物质都会发生反应。这些反应通常会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水含水层的汽油。用目前的模型来预测反应的持续时间或速率是非常困难的，主要是因为反应物混合不良。这定义了一个重要的理论和实践问题，因为大多数当前的水文系统反应输运模型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充分混合假设之上的。为了在这样的系统中做出可靠的预测，对于科学家和工程师，以及最终在环境污染和补救等领域工作的决策者，利益相关者和政策制定者来说，新颖和改进的方法至关重要。然而，混合限制反应的问题远远超出了推动这一提议的水文例子。最近的研究表明，混合限制反应在大范围的地球系统中起主导作用，包括大气中的反应（如臭氧产生）、饮用水含水层中的反应（如污染物的修复）、地质盆地中的反应（如石油生成）、岩浆、热液区和矿体中的反应。该项目将应用于许多领域，包括与气候变化有关的大气反应，生态和微生化系统。研究人员开发了新的计算机模型，证明了在不完全混合系统中模拟反应的新范式的必要性。首先，该项目将应用“时间从属”的理论方法，该方法可以解释随机粒子迁移到活性反应位点的时间。从属关系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。其次，该项目将开发一种随机连续体方法来跟踪浓度扰动的增长。这些干扰包括低浓度区域，这是减慢反应速率的关键。第三，该项目将建立在新的计算机模型上，这些模型被证明是正确的，目的是对理论结果进行基准测试，并促进大规模的反应模拟。所有的方法都将通过详细的数学分析和应用于充分研究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.