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首页> 外文学位 >Contaminant transport in high-capacity pumping setting with a vertical groundwater flow component: Field tracer experiments and numerical modeling.
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Contaminant transport in high-capacity pumping setting with a vertical groundwater flow component: Field tracer experiments and numerical modeling.

机译：在具有垂直地下水流分量的大容量抽水环境中的污染物迁移：现场示踪剂实验和数值模型。

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This study investigates the extent and impact of vertical flow on solute transport in groundwater at the Nebraska MSEA site. Three tracer tests, designed with a geometrical configuration suitable for the detection of vertical flow, were conducted. As the tracer plume moved towards the extraction wells, it bifurcated into two plumes, with the deeper plume travelling at a velocity two to four times higher than the shallow plume. The deeper plume exhibited a vertical displacement of 4 in over a horizontal distance of 13 m.; Multilevel slug tests, grain size analyses, and pumping tests were performed to produce a three-dimensional hydraulic conductivity data base. Preferential pathways for contaminant movement were identified. A low conductivity zone was observed above the 7.3 m depth; while a high conductivity zone was observed towards the aquifer base. The inverse distance weighted technique was used to interpolate hydraulic conductivity values at locations for which measured values were not available.; Three-dimensional flow and transport modeling was used to simulate tracer test 3. The model predictions were found to be strongly sensitive to the variability of hydraulic conductivity and the anisotropy ratio, moderately sensitive to porosity, and least sensitive to dispersivity. The quality of simulations was similar to those reported by Yeh et al. (1995). Peak arrival time was better replicated by the MSEA model, while Yeh et al. model replicated peak relative concentration more accurately. Simulation results were also compared with observed data using temporal moments. The model predicted average travel time more accurately as compared to the absolute integral area.; The MSEA model was able to replicate the bulk movement of the plume with higher degree of certainty than the predictions at individual measurement points. The magnitude of vertical mixing observed implies that the prediction of contaminant transport in agricultural settings must incorporate two key factors: (a) vertical displacement of contaminant trajectories due to pumping for irrigation, and (b) preferential pathways created by aquifer heterogeneity.
机译：这项研究调查了内布拉斯加州MSEA站点垂直流对地下水溶质运移的程度和影响。进行了三种示踪剂测试，这些测试剂设计成适合检测垂直流的几何构型。当示踪剂羽流移向提取井时，它分成两个羽流，较深的羽流以比浅羽流高2-4倍的速度传播。较深的羽流在13 m的水平距离上显示4 in的垂直位移；进行了多段塞测试，粒度分析和抽水测试，以生成三维水力传导率数据库。确定了污染物移动的优先途径。在7.3 m深度以上观察到一个低电导率区；同时观察到朝向含水层底部的高电导率区域。反向距离加权技术用于在无法获得测量值的位置插值水力传导率值。使用三维流动和传输模型来模拟示踪剂测试3。发现模型预测对水力传导率和各向异性比的变化非常敏感，对孔隙度中等敏感，对分散性最不敏感。模拟的质量与Yeh等人报道的相似。 （1995）。 MSEA模型可以更好地复制峰到达时间，而Yeh等人（2007）。模型可以更准确地复制峰相对浓度。还使用时间矩将模拟结果与观察到的数据进行了比较。与绝对积分面积相比，该模型可以更准确地预测平均行驶时间。 MSEA模型能够以比单个测量点的预测更高的确定性来复制羽流的整体运动。观察到的垂直混合的幅度意味着，在农业环境中污染物迁移的预测必须包括两个关键因素：（a）由于灌溉灌溉而造成的污染物轨迹的垂直位移，以及（b）含水层非均质性产生的优先路径。

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