Dynamic Repellency, Wettability and Capillarity as Primary Drivers for Water Flow and Chemical Transport in Soils and Groundwater in the Critical Zone

从土壤表面向下延伸到区域地下水位以下的临界区支持着几乎所有的陆地生命，并包含大部分陆地生物量。我们能够更好地定量预测地下水中的水流、化学运动和气体交换，这对于准确评估许多环境问题以及相关的管理和/或补救方案至关重要。鉴于我们对即将到来的气候变化对温度和降水的影响的最佳估计，更好地从根本上了解控制水的运动以及土壤和地下水中化学污染物的去向和迁移的机制和过程比以往任何时候都更加紧迫。当地下同时存在空气(气相)和水(多相流体)时，我们目前定量预测水流、污染物传输的知识和能力仍然非常有限。对于非饱和土壤和被困在临界区浅层地下水中的空气就是如此，当土壤和岩石的润湿性/排斥性是动态的(依赖于时间)时，这种情况尤其有限。当泄漏的污染物具有表面活性(表面活性)性质时，它受到严格的限制。例如，具有特殊敏感性的土壤是高有机质含量的憎水干燥土壤、野火后土壤以及被石油产品和工业溶剂污染的土壤。由于许多环境污染物和天然化合物作为表面活性化合物(表面活性剂)，大大改变了气水界面的表面张力、固体表面的润湿性和接触角，使得润湿性和毛细管随时间变化的问题变得复杂起来。我拥有丰富的研究经验和长期的国际声誉，在溶质浓度依赖的毛细管、接触角动力学和土壤水分行为的润湿性分数效应方面进行了创新研究和发表文章。这些贡献、知识和专长是拟议研究的基础。科学方法将结合仪器良好的实验室流动池实验、数学模型开发和实地研究。未来5年的主要目标成果将是开发概念验证数据集、概念模型、一阶动态水力函数以及表达动态润湿性和毛细作用的土壤水分渗透和保持的定量一阶数学模型。这项研究将为专家和非专家(如环境修复专家、森林专家、生态水文学家)提供简单的一阶实用模型，以便能够计算更准确和可靠的水渗透、污染物迁移行为和由此产生的土壤水分保持、地下水补给、污染物迁移和去向。

The critical zone which extends form the soil surface down to groundwater below the regional water table supports almost all terrestrial life and contains most of the terrestrial biomass. Our ability to better quantitatively predict water flow, chemical movement and gas exchange in the subsurface is essential and foundational to accurately assessing many environmental problems and associated management and/or remediation schemes. A better fundamental understanding of mechanisms and processes controlling the movement of water and the fate and transport of chemical contaminants in the soil and groundwater is ever more urgent given our best estimates of pending climate change impacts on temperatures and precipitation. Our current knowledge and ability to quantitatively predict water flow, contaminant transport remain critically limited when both air (gas-phase) and water coexist (multi-phase fluids) in the subsurface.  This is the case in unsaturated soils and entrapped air in shallow groundwaters of the critical zone, and particularly limited when the wettability/repellency of the soils and rocks is dynamic (time-dependent). It is critically limited when spilled contaminants have surface active (surfactant) properties.  Examples of soils which are exceptionally sensitive are water repellent dry soils with high organic matter contents, post wildfire soils, and soils contaminated by petroleum products and industrial solvents. The problem of wettability and capillarity changing over time are complicated by the fact that numerous environmental contaminants and naturally occurring compounds act as surface active compounds (surfactants) which substantially change the surface tension at the air water interface, the wettability and contact angle at solid surfaces. I have extensive research experience and a long international reputation for my innovative research and publications on solute concentration dependent capillarity, contact angle dynamics and fractional wettability effects on soil water behavior. Those contributions, knowledge and expertise are foundational to the proposed research. The scientific approach will combine well instrumented laboratory-based flow cell experiments, mathematical model development, and field studies. The primary targeted outcomes over the next 5 years will be to develop proof of concept data sets, conceptual models, first-order dynamic hydraulic functions and quantitative first-order mathematical models of water infiltration and retention in soils expressing dynamic wettability and capillarity. The research will generate simple first-order practical models for specialists and non-specialists (e.g. environmental remediation specialists, foresters, eco-hydrologists) to be able to calculate more accurate and reliable water infiltration, contaminant transport behaviours and resultant soil water retention, groundwater recharge and contaminant migration and fate.