Chaotic advection and reaction during engineered injection and extraction in heterogeneous porous media
Chaotic advection and reaction during engineered injection and extraction in heterogeneous porous media
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DOI：
10.1002/2013wr014057
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发表时间：
2014-02
影响因子：
5.4
通讯作者：
R. Neupauer;J. Meiss;D. Mays
中科院分区：
文献类型：
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作者：
R. Neupauer;J. Meiss;D. Mays
在污染地下水的原位修复过程中，通常将处理溶液注入污染区域以引发降解污染物的反应。降解反应仅发生在处理溶液和受污染的地下水足够接近以至于混合会将它们混合在一起的情况下。当处理溶液扩散到污染区域时，降解会增强，从而增加混合和降解反应的空间范围。扩散是由含水层异质性和驱动水流的外部强迫的空间变化引起的局部速度变化造成的。外部强迫的某些模式已被证明会产生混沌平流，众所周知，这会增强地下水流和其他层流中溶质的扩散。这项工作使用流动和反应输运的数值模拟来研究含水层异质性如何改变含水层中混沌平流的定性和定量方面，以及这些变化增强污染物降解的程度。我们使用工程注入和提取（EIE）产生混沌平流，这种方法在污染区域周围的井中顺序注入和提取水，以创建促进羽流扩散的时间依赖性流场。我们证明，随着异质性程度的增加，羽流扩散和污染物降解都会增加；然而，相对于羽流扩散的增加，污染物降解的增加很小。我们的结果表明，EIE 和异质性的综合作用比单独作用产生的拉伸要大得多。
During in situ remediation of contaminated groundwater, a treatment solution is often injected into the contaminated region to initiate reactions that degrade the contaminant. Degradation reactions only occur where the treatment solution and the contaminated groundwater are close enough that mixing will bring them together. Degradation is enhanced when the treatment solution is spread into the contaminated region, thereby increasing the spatial extent of mixing and degradation reactions. Spreading results from local velocity variations that emerge from aquifer heterogeneity and from spatial variations in the external forcings that drive flow. Certain patterns in external forcings have been shown to create chaotic advection, which is known to enhance spreading of solutes in groundwater flow and other laminar flows. This work uses numerical simulations of flow and reactive transport to investigate how aquifer heterogeneity changes the qualitative and quantitative aspects of chaotic advection in an aquifer, and the extent to which these changes enhance contaminant degradation. We generate chaotic advection using engineered injection and extraction (EIE), an approach that uses sequential injection and extraction of water in wells surrounding the contaminated region to create time‐dependent flow fields that promote plume spreading. We demonstrate that as the degree of heterogeneity increases, both plume spreading and contaminant degradation increase; however, the increase in contaminant degradation is small relative to the increase in plume spreading. Our results show that the combined effects of EIE and heterogeneity produce substantially more stretching than either effect separately.