The impact of physical heterogeneity and connectivity on LNAPL entrapment and dissolution

物理异质性和连通性对 LNAPL 截留和溶解的影响

• 批准号: 0408895
• 负责人: Stephen Silliman
• 金额: --
• 依托单位: University of Notre Dame
• 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: 2004-07-01 至 2008-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0408895&HistoricalAwards=false
• 关键词: impact; physical; heterogeneity; connectivity; LNAPL

0408895SillimanThis work examines the transport behavior of LNAPLs in the region bounding thewater table. Defined as the Partially Saturated Fringe, or PSF (Berkowitz et al., 2003),the region bounding the water table includes the classic Capillary Fringe (CF) and theregion below the water table in which multiple phases (air, water, and/or LNAPL) arepresent. This work builds on prior work within our laboratory on Air Entry Barriers (e.g.,Silliman et al., 2002; Dunn and Silliman, 2003; Dunn et al., 2003) as well as thesubstantial literature on LNAPL behavior (e.g., Nambi and Powers, 2000; Illangasekareet al., 1995a,b; Schroth et al., 1998; Walser et al., 1999; Van Dijke and Van Der Zee,1997). Of particular interest for the present study is the interaction of the structure ofheterogeneity and the distribution / dissolution of LNAPLs under conditions of afluctuating water table. The work is based on a combination of two-dimensionallaboratory and numerical experiments on the distribution of pure- and dissolved-phaseLNAPL in a two-zone porous medium (coarse sand and fine sand). Within thelaboratory, visual and TDR techniques will be used to monitor LNAPL saturation. Massof dissolved-phase LNAPL constituents will be monitored at the outflow from the porousmedia. Numerical experiments will be performed on simulated random and scaledporous media and T2VOC, an extension of TOUGH2 [Transport Of UnsaturatedGroundwater and Heat, version II], developed at Lawrence Berkeley NationalLaboratory. These experiments will be based on generating a series of realizations ofrandom distributions of the coarse and fine sands (based on both stationary randompermeability distributions and structured permeability distributions), followed bysimulation of a fluctuating water table with significant LNAPL phase above the originalwater table. The laboratory experiments will be utilized to verify LNAPL behavior aspredicted by the numerical model, as well as to provide visualization of LNAPLbehavior. The numerical model will be utilized to address the central hypotheses:The degree of connectivity (defined within the proposal) of coarse sand lenseswithin a fine sand matrix will influence the amount of LNAPL entrapped withinthe PSF. Specifically, as the connectivity of the coarse regions increases (with thesame relative volume of coarse and fine sands), the volume of entrapped LNAPLwill decrease. An increase in the degree of connectivity of coarse sand lenses within a fine sandmatrix will result in a reduced overall rate of dissolution of LNAPL entrappedwithin the PSF.In terms of intellectual merit, this work advances the understanding of controls ofLNAPL distribution and dissolution in the PSF. From a theoretical standpoint, thisprovides greater insight into the impact of physical structure on transport characteristicsnear the water table. From an applied standpoint, extension of this work holds promisefor innovative means of remediation of LNAPL contaminated systems.In terms of broader impact, this work will provide training for one Ph.D. and oneMasters student, as well as contributing to undergraduate and graduate courses ingroundwater hydrology and remediation. In addition, this work will aid in furtherdevelopment of research collaborations with colleagues in western Africa (Benin).

[408895silliman]这项工作考察了LNAPLs在地下水位边界区域的输运行为。被定义为部分饱和条纹或PSF (Berkowitz et al., 2003)，水位边界区域包括经典的毛细条纹（CF）和水位以下的多相（空气、水和/或LNAPL）代表的区域。这项工作建立在我们实验室之前关于空气进入障碍的工作（例如，Silliman等人，2002年；Dunn和Silliman， 2003年；Dunn等人，2003年）以及关于LNAPL行为的大量文献（例如，Nambi和Powers， 2000年；Illangasekareet等人，1995年；Schroth等人，1998年；Walser等人，1999年；Van Dijke和Van Der Zee，1997年）。本研究特别感兴趣的是在波动的地下水位条件下，非均质结构与LNAPLs分布/溶解的相互作用。这项工作是基于二维实验室和数值实验的结合，研究了纯相和溶相elnapl在两区多孔介质（粗砂和细砂）中的分布。在实验室中，视觉和TDR技术将用于监测LNAPL饱和度。从多孔介质流出处监测溶解相LNAPL组分的质量。数值实验将在模拟随机和尺度多孔介质和T2VOC上进行，T2VOC是由劳伦斯伯克利国家实验室开发的TOUGH2[非饱和地下水和热量输送，第二版]的扩展。这些实验将基于生成粗砂和细砂随机分布的一系列实现（基于平稳随机渗透率分布和结构化渗透率分布），然后模拟具有显著LNAPL相的波动地下水位高于原始地下水位。实验室实验将用于验证数值模型预测的LNAPL行为，并提供LNAPL行为的可视化。数值模型将用于解决中心假设：细砂基质内粗砂透镜的连通性程度（在提案中定义）将影响被困在PSF内的LNAPL的数量。具体来说，随着粗砂区连通性的增加（粗砂和细砂的相对体积相同），被困lnapl的体积将减少。细砂基质内粗砂透镜连通性的增加将导致包裹在PSF内的LNAPL的整体溶解速率降低。就智力价值而言，这项工作促进了对PSF中flnapl分布和溶解的控制的理解。从理论的角度来看，这提供了更深入地了解物理结构对地下水位附近运输特征的影响。从应用的角度来看，这项工作的扩展有望为LNAPL污染系统的修复提供创新手段。就更广泛的影响而言，这项工作将为一名博士和一名硕士学生提供培训，并为地下水水文学和修复的本科和研究生课程做出贡献。此外，这项工作将有助于进一步发展与西非（贝宁）的同事的研究合作。