Insights into effects of discharge ratio on flow characteristics and pollutant transport in a Y-shaped open channel confluence with emergent rigid vegetation

Xiaodong Liu; Xuneng Tong; Ting Yang; Sanjeeb Mohapatra; Zulin Hua; Yuan Zhang; Kejian Chu; Hongqin Xue

doi:10.1016/j.jenvman.2023.117421

Insights into effects of discharge ratio on flow characteristics and pollutant transport in a Y-shaped open channel confluence with emergent rigid vegetation

J Environ Manage. 2023 Apr 15:332:117421. doi: 10.1016/j.jenvman.2023.117421. Epub 2023 Feb 4.

Authors

Xiaodong Liu¹, Xuneng Tong², Ting Yang³, Sanjeeb Mohapatra⁴, Zulin Hua¹, Yuan Zhang⁵, Kejian Chu¹, Hongqin Xue⁶

Affiliations

¹ Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China; Yangtze Institute for Conservation and Development, Hohai University, Jiangsu 210098, China.
² Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China; Department of Civil and Environmental Engineering, National University of Singapore, 1 Engineering Drive 2, Singapore, 117576, Singapore. Electronic address: xunengtong@u.nus.edu.
³ Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China; Jiangsu Jinling Environment Co., Ltd., Nanjing 211100, China.
⁴ NUS Environmental Research Institute, National University of Singapore, 1 Create way, Create Tower, #15-02, Singapore 138602, Singapore.
⁵ Key Laboratory of Integrated Regulation and Resource Development on Shallow Lakes of Ministry of Education, College of Environment, Hohai University, Nanjing 210098, China.
⁶ School of Civil Engineering, Nanjing Forestry University, Nanjing 210037, China.

PMID: 36739776
DOI: 10.1016/j.jenvman.2023.117421

Abstract

Turbulence generated within the vegetated confluence system is important for water quality and river management. In this study, we conducted a series of experiments to explore the extent to which emergent rigid vegetation in the confluence channel influences hydrodynamic characteristics and contaminant transport. First, a series of tests with increasing discharge ratios (from 0.35, 0.5, and 1) was conducted to quantify the effects of the discharge ratio on hydrodynamic conditions within the vegetated confluence. Then, tests with different discharge ratios were also set up to explore how contaminants released locations and modes (line and point source) influence the transport and mixing of contaminants. The results showed that increasing the discharge ratio induced larger momentum in the confluence area. The increase in discharge ratio rendered the circulation stronger, and its position came earlier in the non-vegetative area. In addition, the dimensionless turbulent kinetic energy peaked near the interface of the non/vegetated zone. With the increase in the discharge ratio, the dimensionless turbulent kinetic energy was found to be smaller. In the contaminants transport tests, the results revealed larger discharge ratio could speed up contaminants transport and mixing. The applications from this study would be helpful to pollutant transport management in natural confluences.

Keywords: Contaminants transport; Flow characteristics; Longitudinal dispersion; Rigid emerged vegetation; Turbulent kinetic energy; Y-shaped confluence channel.

MeSH terms

Environmental Pollutants*
Hydrodynamics
Rivers
Water Quality*

Substances

Environmental Pollutants