Collaborative Research: Fusion of Tomography Tests for DNAPL Source Zone Characterization: Technology Development and Validation

[229713]低密度非水相液体（DNAPLs）在世界各地的许多地方都很普遍。多变的释放历史和地质非均质性使得DNAPLs在源区分布复杂。这些源区可能造成数十年至数百年的长期地下水污染。因此，需要对源区存在的DNAPLs的空间分布、质量和组成进行详细的表征，以便设计有效的修复方案。在过去的几年里，许多示踪技术已经被引入来增强DNAPL源区的表征。虽然这些示踪技术允许原位估计DNAPL饱和度的体积平均值，但迫切需要开发一种具有成本效益的技术，以高分辨率表征DNAPL的空间分布。本研究的目标是：1)开发一个软件/硬件包，使用随机方法融合不同类型的信息，为DNAPL源区提供具有成本效益的表征、监测和预测工具；2)进行实验室实验来测试和验证该技术；3)分发研究结果，以帮助科学家、工程师和管理人员解决DNAPL污染问题。智力优势：提出了新的数据处理技术，随机信息融合，以迭代的方式结合在不同地点不同尺度上的不同类型的测量，以提供对DNAPL残差分布及其不确定性的最佳估计。具体来说，它分析了水力断层成像的信息，首先在三维上识别水力非均质性。然后，通过结合从保守示踪层析获得的新信息，改进了对异质性的估计。之后，利用改进的水力非均质性估计来模拟水力层析成像，从而获得有关地下响应的更详细信息。这些新信息再次反馈到技术中，以更新水力非均质性的估计。迭代过程继续进行，直到所有可用的信息和测量都被充分利用，以确定控制dnapl空间分布的过程和变量。完成后，将新获得的过程和变量知识与分区示踪层析成像获得的数据相结合，以有效地描绘源区DNAPL残余饱和度的空间分布。所提出的层析成像技术和随机信息融合算法将在沙盒中进行测试和验证。所提出的研究的成功不仅推动了一般的估计理论，而且也推动了我们表征和监测地下的技术。更广泛的影响：提出的随机融合技术可以在不同的地质条件下与不同的表征技术相结合。它也适用于DNAPL源区表征的所有阶段，包括初始筛选、场地表征、修复和长期监测。一个基于网络的虚拟水力/示踪层析实验室将被创建，并可供世界各地的任何学生、教育工作者、从业者和研究人员使用。我们相信这个虚拟实验室将激发创造力，不仅对经典的地下水文学，而且对水文科学的其他学科都有革命性的影响。例如，使用我们的随机信息融合技术，人们可能能够吸收气象信息，如照明和降水，作为大尺度地下环境层析成像调查的替代激励源。

0229713IllmanDense Nonaqueous Phase Liquids (DNAPLs) are prevalent at a large number of sites throughout the world. The variable release history and geologic heterogeneity make the distribution of DNAPLs in the source zone complex. These source zones can contribute to long-term groundwater contamination for decades to centuries. Therefore, the spatial distribution, mass, and composition of DNAPLs present in the source zone need to be characterized in great detail so that efficient remediation schemes can be designed. During the last few years, many tracer techniques have been introduced to enhance the characterization of DNAPL source zones. While these tracer techniques allow for the in situ estimation of volume-averaged values of DNAPL saturation, there is an urgent need for the development of a cost-effective technology to characterize the spatial distribution of DNAPLs at high resolutions.The objectives of this proposed study are: 1) to develop a software/hardware package that fuses different types of information using a stochastic approach to provide a cost-effective characterization, monitoring, and predictive tool for the DNAPL source zone, 2) to conduct laboratory experiments to test and verify this proposed technology, and 3) to distribute the results of the research to assist scientists, engineers, and managers to solve DNAPL contamination problems. Intellectual Merit: The proposed new data processing technique, stochastic information fusion, combines different types of measurements taken at different locations over different scales in an iterative manner to provide the best estimate of the DNAPL residual distribution and its uncertainty. Specifically, it analyzes the information derived from hydraulic tomography to identify hydraulic heterogeneity first in three-dimensions. It then improves the estimate of the heterogeneity by incorporating new information acquired from the conservative tracer tomography. Afterward, the improved estimate of hydraulic heterogeneity is used to simulate the hydraulic tomography such that more detailed information about the response of the subsurface becomes available. This new information again is fed back to the technique to update the estimate of hydraulic heterogeneity. The iterative process continues until all available information and measurements are fully utilized in identifying the processes and variables that control the spatial distribution of DNAPLs. Upon completion, the newly derived knowledge of the processes and variables are then combined with data derived from the partitioning tracer tomography to effectively delineate the spatial distribution of DNAPL residual saturation in the source zone. The proposed tomography technique and the stochastic fusion of information algorithm are to be tested and validated in a sandbox. Success of the proposed research advances not only estimation theory in general but also our technologies for characterizing and monitoring the subsurface.Broader Impacts: The proposed stochastic fusion technology can be integrated with different characterization techniques in diverse geological conditions. It is also amenable to all stages of DNAPL source zone characterization including initial screening, site characterization, remediation, and long-term monitoring. A web-based virtual hydraulic/tracer tomography laboratory will be created and be available to any student, educator, practitioner, and researcher around the world. We believe this virtual laboratory will stimulate creativity to revolutionize not only classical subsurface hydrology but also other disciplines of hydrologic sciences. For example, using our stochastic information fusion technology, one may be able to assimilate meteorological information such as lighting and precipitation as alternative excitation sources for tomographic surveys of the subsurface environment at large scalesseeing into the earth.