Department of Environmental Sciences and Engineering, University of North Carolina, Chapel Hill, NC 27599-7431, USA.
J Contam Hydrol. 2010 Jun 25;115(1-4):46-63. doi: 10.1016/j.jconhyd.2010.03.005. Epub 2010 Apr 14.
The behavior of dense, viscous calcium bromide brine solutions used to remediate systems contaminated with dense nonaqueous phase liquids (DNAPLs) is considered in laboratory and field porous medium systems. The density and viscosity of brine solutions are experimentally investigated and functional forms fit over a wide range of mass fractions. A density of 1.7 times, and a corresponding viscosity of 6.3 times, that of water is obtained at a calcium bromide mass fraction of 0.53. A three-dimensional laboratory cell is used to investigate the establishment, persistence, and rate of removal of a stratified dense brine layer in a controlled system. Results from a field-scale experiment performed at the Dover National Test Site are used to investigate the ability to establish and maintain a dense brine layer as a component of a DNAPL recovery strategy, and to recover the brine at sufficiently high mass fractions to support the economical reuse of the brine. The results of both laboratory and field experiments show that a dense brine layer can be established, maintained, and recovered to a significant extent. Regions of unstable density profiles are shown to develop and persist in the field-scale experiment, which we attribute to regions of low hydraulic conductivity. The saturated-unsaturated, variable-density groundwater flow simulation code SUTRA is modified to describe the system of interest, and used to compare simulations to experimental observations and to investigate certain unobserved aspects of these complex systems. The model results show that the standard model formulation is not appropriate for capturing the behavior of sharp density gradients observed during the dense brine experiments.
用于修复被稠密非水相液体（DNAPL）污染的系统的稠密、粘性溴化钙盐水溶液的行为在实验室和现场多孔介质系统中进行了研究。通过实验研究了盐水溶液的密度和粘度，并在很宽的质量分数范围内拟合了函数形式。在溴化钙质量分数为 0.53 时，获得了密度是水的 1.7 倍，相应的粘度是水的 6.3 倍。使用三维实验室单元研究了在受控系统中分层稠密盐水层的建立、持续存在和去除速率。在多佛国家测试场进行的现场规模实验的结果用于研究建立和维持作为 DNAPL 回收策略一部分的稠密盐水层的能力，以及以足够高的质量分数回收盐水，以支持盐水的经济再利用。实验室和现场实验的结果均表明，可以在很大程度上建立、维持和回收稠密盐水层。现场规模实验中显示出不稳定的密度分布区域的发展和持续存在，我们将其归因于低水力传导率区域。修改了饱和-非饱和、变密度地下水流动模拟代码 SUTRA，以描述相关系统，并将模拟结果与实验观察结果进行比较，以研究这些复杂系统的某些未观察到的方面。模型结果表明，标准模型公式不适用于捕获在稠密盐水实验中观察到的急剧密度梯度的行为。
