School of Earth Sciences and Engineering, Hohai University, Nanjing 211100, China.
Int J Environ Res Public Health. 2021 Jan 18;18(2):762. doi: 10.3390/ijerph18020762.
The coupled effect of seawater intrusion and inland freshwater recharge plays an important role in contamination transport in coastal heterogeneous aquifer. In this study, the effects of seawater intrusion and inland recharge on contamination transport were investigated by conducting laboratory experiments and numerical simulations. The laboratory tests were conducted in a sand tank considering two scenarios, namely the conditions of landward and seaward hydraulic gradients. The SEAWAT software was applied for validating the contaminant transport in coastal heterogeneous aquifer. The results indicated that the simulated seawater wedge and contours of the saltwater contaminant matched the observed ones well. The length of the seawater wedge in the scenario of seaward hydraulic gradient was smaller than that in the scenario of landward hydraulic gradient, which reflected that the large quantity of inland recharge have a negative effect on the invasion process of seawater. The plume moved mainly downward in the heterogeneous unconfined aquifer for both scenarios. The pollution plume became concave at the interface between each two layers, which was because the velocity of contaminant plume migration increased gradually from the upper layer to lower layer. The migration direction of the front of the plume was consistent with the direction of hydraulic gradient, which indicated that it was influenced by the water flowing. The maximum area of plume in the scenario of seaward hydraulic gradient was slightly smaller than that in the scenario of landward hydraulic gradient. The maximum area and vertical depth of the pollutant plume were sensitive to the hydraulic conductivity, dispersivity and contamination concentration. This study was of great significance to the controlling of pollution and utilization of freshwater resources in coastal areas.
海水入侵和内陆淡水补给的耦合效应对沿海非均质含水层中污染物的运移起着重要作用。本研究通过实验室实验和数值模拟研究了海水入侵和内陆补给对污染物运移的影响。实验室测试在考虑两个情景的砂箱中进行，即内陆水力梯度和沿海水力梯度的条件。应用 SEAWAT 软件验证了沿海非均质含水层中的污染物运移。结果表明，模拟的海水楔和咸水污染物的轮廓与观测值吻合较好。在沿海水力梯度情景下，海水楔的长度小于内陆水力梯度情景下的长度，这反映了大量内陆补给对海水入侵过程有负面影响。在两种情况下，污染羽流主要在非承压含水层中向下移动。在每个两层之间的界面处，污染羽流变得凹形，因为污染物羽流迁移速度从上层逐渐增加到下层。羽流前缘的迁移方向与水力梯度的方向一致，这表明它受到水流的影响。在沿海水力梯度情景下，羽流的最大面积略小于内陆水力梯度情景下的最大面积。污染羽流的最大面积和垂直深度对水力传导率、弥散度和污染浓度敏感。本研究对沿海地区的污染控制和淡水资源利用具有重要意义。
