Abstract
The mixing degree upstream of the diverging area is one of the important factors influencing the pollutant allocation characteristics of braided rivers, but the effect remains unclear at present. In this paper, physical model tests were designed to study the effect on the pollutant flux ratio with six branching forms and a series of longitudinal discharge distances. The results indicated that the mixing degree upstream of the diverging area, which is closely related to the longitudinal discharge distance, notably affected the pollutant flux ratio. The lower the mixing degree, the larger was the deviation of the pollutant flux ratio from the discharge ratio. Moreover, a linear relationship was attained between the dimensionless mixing degree and the dimensionless deviation of the pollutant flux ratio from the discharge ratio. Consideration of different branching angles or different water layers or different branches did not affect this trend. The experimental results further demonstrated that the intercept and slope of the aforementioned linear relationship depended on the branching angle and exhibited an opposite monotonicity with a symmetric branch angle as the dividing point. These results help towards a better understanding of the mechanism of the factors influencing pollutant transport in complicated braided rivers, and provide a new approach to predicting the pollutant flux ratio of braided rivers.
Abstract
目的
分汊河流支汊间的污染物分配规律具有重要意义。同时, 分污特性受诸多因素影响, 因此较为复杂。本文旨在探讨在具有分汊结构的河流中, 分流区前污染物混合度对下游支汊分污比的影响。研究与排放位置相关的混合度的定义、量化以及与分污比的规律关系, 以进一步认识分汊河流污染物扩散影响因素的作用机制。
创新点
1. 建立水质物理模型, 得到在排放位置影响下支汊分污比的变化情况。2. 基于高斯分布, 定义分流区前混合度, 并得到无量纲化的混合度与分污比偏离量的线性关系。3. 得出在线性关系中线性系数受分汊角的影响情况。
方法
1. 建立包含6种分汊形式与多种排放位置的水质物理模型, 得到排放位置与分污比的关系（图9~14）；2. 基于分流区前断面浓度分布的试验成果, 借助高斯分布公式定义分流区前混合度（图16）；3. 通过无量纲化处理, 得到分流区前混合度与分污比偏离量的关系（图18~29）。4. 通过数据分析, 构建线性关系中的系数与分汊角的关系。
结论
1. 与纵向排放距离高度相关的分流区前混合度显著影响分污比；混合度越低, 分污比偏离相应分流比的幅度越大。2. 无量纲化的混合度与无量纲化的分污比偏离量呈现近似线性关系。3. 线性关系中的截距和斜率与分汊角相关, 并以对称分汊角为界呈现相反的单调性。
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References
Alexeevsky NI, Chalov RS, Berkovich KM, et al., 2013. Channel changes in largest Russian rivers: natural and anthropogenic effects. International Journal of River Basin Management, 11(2):175–191. https://doi.org/10.1080/15715124.2013.814660
Chalov S, Moreido V, Sharapova E, et al., 2020. Hydrodynamic controls of particulate metals partitioning along the Lower Selenga river—main tributary of the Lake Baikal. Water, 12(5):1345. https://doi.org/10.3390/w12051345
Chalov SR, Alexeevsky NI, 2015. Braided rivers: structure, types and hydrological effects. Hydrology Research, 46(2):258–275. https://doi.org/10.2166/nh.2013.023
Das A, Barman BC, Nandi N, 2022. On some aspects of flow characteristics of the bifurcated channel-an experimental approach. ISH Journal of Hydraulic Engineering, in press. https://doi.org/10.1080/09715010.2022.2042862
Gu L, Hua ZL, Chu KJ, et al., 2011a. Experimental study on transport characteristics of pollutants with different density in braided river. Journal of Hydroelectric Engineering, 30(6):242–250 (in Chinese).
Gu L, Hua ZL, Zhang CK, et al., 2011b. Mixing characteristics and transport flux ratio of pollutants in braided rivers. Fresenius Environmental Bulletin, 20(9):2315–2325.
Hua ZL, Gu L, 2008. Experiments on pollutant transport of centerline discharge into the braided river. Proceedings of the 16th IAHR-APD Congress and the 3rd Symposium of IAHR-ISHS. https://doi.org/10.1007/978-3-540-89465-0_96
Hua ZL, Peng J, Ji W, et al., 2013a. Modeling experiment on characteristics of pollutant transport and mixing in waterway with multi-anabranch and Five Islets. Environmental Science & Technology, 36(8):6–10 (in Chinese).
Hua ZL, Ji W, Shan NN, et al., 2013b. Pollutant mixing and transport process via diverse transverse release positions in a multi-anabranch river with three braid bars. Water Science and Engineering, 6(3):250–261. https://doi.org/10.3882/j.issn.1674-2370.2013.03.002
Ji W, Hua ZL, Wu W, et al., 2012. Transport and mixing characteristics of pollutants by continuous point source discharge in the multi-anabranch river with Three Braid Bars. Proceedings of the International Conference on Biomedical Engineering and Biotechnology. https://doi.org/10.1109/iCBEB.2012.454
Jiang F, Chen WP, Chen M, et al., 2006. Primary study on diffusion of contaminants in meandering furcated rivers. Water Resources Protection, 22(4):30–32 (in Chinese). https://doi.org/10.3969/j.issn.1004-6933.2006.04.008
Lee ME, Seo IW, 2007. Analysis of pollutant transport in the Han River with tidal current using a 2D finite element model. Journal of Hydro-environment Research, 1(1):30–42. https://doi.org/10.1016/joher.2007.04.006
Leopold LB, Wolman MG, 1957. River Channel Patterns: Braided, Meandering, and Straight. USGS Numbered Series, U.S. Government Printing Office, Washington, USA. https://doi.org/10.3133/pp282B
Li KF, Zhao WQ, 1994. Study on diffusion and mixing law of pollutants in braided river. Water Resources Protection, (1):8–12 (in Chinese).
Lu HY, Li ZW, Hu XY, et al., 2022. Morphodynamic processes in a large gravel-bed braided channel in response to runoff change: a case study in the source region of Yangtze River. Arabian Journal of Geosciences, 15(5):377. https://doi.org/10.1007/s12517-022-09641-y
Okuyade WIA, Abbey TM, 2016. Pollutants spread in a bifurcating river: the River Nun, Bayelsa, Nigeria. Journal of Scientific Research and Reports, 12(6):1–19. https://doi.org/10.9734/JSRR/2016/26722
Peng FJ, Li KF, Liang RF, et al., 2021. Shallow lake water exchange process before and after water diversion projects as affected by wind field. Journal of Hydrology, 592:125785. https://doi.org/10.1016/j.jhydrol.2020.125785
Redolfi M, 2015. Sediment Transport and Morphology of Braided Rivers: Steady and Unsteady Regime. PhD Thesis, Queen Mary University of London, London, UK.
Yang HY, Lin BL, Zhou JJ, 2015. Physics-based numerical modelling of large braided rivers dominated by suspended sediment. Hydrological Processes, 29(8):1925–1941. https://doi.org/10.1002/hyp.10314
Yun SH, Seo IW, Kwon SY, 2019. Analysis of analysis of behavior of contaminants at the braided river using the transient storage model. Proceedings of the 38th IAHR World Congress. https://doi.org/10.3850/38WC092019-1174
Acknowledgments
This work is supported by the National Natural Science Foundation of China (No. 51879176) and the Jiangxi Provincial Water Conservancy Science and Technology Project (No. 202022YBKT09), China.
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Jun ZOU designed the research. Jun ZOU and Chang-yuan LI processed the corresponding data. Jian-min ZHANG provided the test scheme reference. Jun ZOU wrote the first draft of the manuscript, and revised and edited the final version.
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Jun ZOU, Jian-min ZHANG, and Chang-yuan LI declare that they have no conflict of interest.
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Effects of the mixing degree upstream of the diverging area on the pollutant allocation characteristics of a Braided River
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Zou, J., Zhang, Jm. & Li, Cy. Effects of the mixing degree upstream of the diverging area on the pollutant allocation characteristics of a braided river. J. Zhejiang Univ. Sci. A 23, 733–744 (2022). https://doi.org/10.1631/jzus.A2100540
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DOI: https://doi.org/10.1631/jzus.A2100540
Key words
- Mixing degree upstream
- Diverging area
- Longitudinal distance
- Deviation of pollutant flux ratio
- Standard deviation
- Linear relationship