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The effect of density-driven flow on the transport of high-concentration solutes in the hyporheic zone |
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| Authors: | Guangqiu Jin Yongfei Hao Jie Wei Yihang Yang Xiaoxiao Shen Hongwu Tang Ling Li |
| Institution: | 1. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China
College of Water Conservancy and Hydropower Engineering, Hohai University, Nanjing, China;2. Power China Zhongnan Engineering Corporation Limited, Changsha, China;3. China Water Huaihe Planning, Design and Research Co. Ltd, Hefei, China;4. College of Agricultural Engineering, HoHai University, Nanjing, China;5. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China;6. School of Engineering, Westlake University, Hangzhou, China |
| Abstract: | In this study, both laboratory experiments and numerical simulations were conducted to investigate the effect of density-driven flow on the transport of high-concentration pollutants in the hyporheic zone. The results show that the density gradient can change the flow of pore water and the strong density-driven flow can lead to an unstable flow, which increases the effect of preferential flow and thus causes the appearance of solute fingers in the hyporheic zone. Notably, these solute fingers become more obvious with the increase of depth. The appearance of solute fingers depends on the relative strength of the pumping exchange and density gradient, which are represented by the dimensionless number M* and N* respectively. Finger flows appear near the interface when M* is less than 0.5 N*. This study may contribute to better understanding the transport and destination of solutes and thus may provide some insights into the assessment on pollution incidents. |
| Keywords: | density-driven flow fingers high solute concentration hyporheic exchange |