Distribution pattern of flocsand and its controlling factors in a saltwater-wedge estuary: A case study of the Modaomen Estuary of the Pearl (Zhujiang) River

Zhang Kaiyun; Liang Hongyue; Wang Pu; Li Haiwei; Wei Wen; Cai Huayang; Liu Feng; Zhu Lei

doi:10.12284/hyxb2024067

Volume 46 Issue 6

Jun. 2024

Turn off MathJax

Article Contents

Article Navigation > Haiyang Xuebao > 2024 > 46(6): 84-97

Zhang Kaiyun，Liang Hongyue，Wang Pu, et al. Distribution pattern of flocsand and its controlling factors in a saltwater-wedge estuary: A case study of the Modaomen Estuary of the Pearl (Zhujiang) River[J]. Haiyang Xuebao，2024, 46(6)：84–97 doi: 10.12284/hyxb2024067

Citation:

PDF( 9007 KB)

Distribution pattern of flocsand and its controlling factors in a saltwater-wedge estuary: A case study of the Modaomen Estuary of the Pearl (Zhujiang) River

doi: 10.12284/hyxb2024067

1.
Institute of Estuarine and Coastal Research, School of Ocean Engineering and Technology, Sun Yat-Sen University, Guangzhou 510275, China
2.
Key Laboratory of Coastal Science and Integrated Management, Ministry of Natural Resources, Qingdao 266061, China
3.
School of Marine Science, Sun Yat-Sen University, Guangzhou 510275, China

Received Date: 2024-02-09
Rev Recd Date: 2024-05-24

Available Online: 2024-07-22

Publish Date: 2024-06-01

Abstract

Abstract

Flocculation of fine sediments is a key process affecting sediment transport and dispersion in estuaries, which is controlled by complex dynamic structure of estuaries, and spatial distribution of flocs in a stratification condition needs to be explored. To solve this problem, in this study, based on the hydrology and sediment cruising observation in the Modaomen Estuary of the Pearl River during the dry season in 2020, spatial and temporal distribution of flocs in the Modaomen Estuary was analyzed, impacts of dynamics factors were investigated, and distribution pattern of flocs in a stratification condition was uncovered. The results show that median floc size in the Modaomen Estuary during the observation period ranged from 1.87 μm to 395.53 μm, and volumetric concentration of flocs ranged from 20.29 μL/L to 1495.67 μL/L. Vertically, median floc size in the middle and surface layers was generally larger than that in the bottom layer. The plane distribution characteristic of the median floc size is that the maximum values generally occurred at the central bar and the west side. Decomposition of multimodal floc size distributions indicates that the flocs in the Modaomen Estuary were composed of primary particles (Pp) and Flocculi (collectively known as Pico-flocs), microflocs (Micro), macroflocs (Macro), among which Macro was dominant. In view of vertical distribution, the volumetric concentration of Pico-flocs and Micro in the bottom layer tended to be larger than that in the surface and middle layers, while volumetric concentration of Macro in the surface and middle layers was generally larger than that in the bottom layer, which is closely related to dynamic structure in the salt water wedge estuary. Strong salinity stratification inhibited the exchange of flocs between different water layers, resulting in a relatively higher percentage of Macro in the surface layer than that in the middle and bottom layers. In the bottom layer flocs were affected by intensity of turbulent shear and deflocculation process was dominant. As a result, the percentage of Pico-flocs and Micro was higher than the surface and middle layers. This study is not only helpful to elucidate the flocculation mechanism of fine sediment under complex dynamics, but also provides technical support for regulation of mouth bar, goverment of water and sediment, and channel dredging in the Modaomen Estuary.
- the Modaomen Estuary,
- decomposition of particle size,
- spatial variation,
- salinity stratification,
- turbulence

FullText(HTML)

References(37)

References

[1]	Milliman J D, Farnsworth K L. River Discharge to the Coastal Ocean: A Global Synthesis[M]. Cambridge: Cambridge University Press, 2011: 384.
[2]	Bronick C J, Lal R. Soil structure and management: areview[J]. Geoderma, 2005, 124(1/2): 3−22.
[3]	Droppo I G, Ongley E D. Flocculation of suspended sediment in rivers of southeastern Canada[J]. Water Research, 1994, 28(8): 1799−1809. doi: 10.1016/0043-1354(94)90253-4
[4]	朱文武, 李九发, 姚弘毅, 等. 长江河口北槽河道悬沙絮团特性及其影响因素研究[J]. 海洋学报, 2016, 38(3): 88−97. doi: 10.3969/j.issn.0253-4193.2016.03.009 Zhu Wenwu, Li Jiufa, Yao Hongyi, et al. Study on sediment floccules and the influence factors in the North Passage of the Changjiang Estuary[J]. Haiyang Xuebao, 2016, 38(3): 88−97. doi: 10.3969/j.issn.0253-4193.2016.03.009
[5]	Manning A J, Baugh J V, Spearman J R, et al. Flocculation settling characteristics of mud: sand mixtures[J]. Ocean Dynamics, 2010, 60(2): 237−253. doi: 10.1007/s10236-009-0251-0
[6]	田枫, 欧素英, 杨昊, 等. 伶仃洋河口泥沙絮凝特征及影响因素研究[J]. 海洋学报, 2017, 39(3): 55−67. doi: 10.3969/j.issn.0253-4193.2017.03.005 Tian Feng, Ou Suying, Yang Hao, et al. Study on the flocs characteristic and dynamics effects in the Lingdingyang Estuary[J]. Haiyang Xuebao, 2017, 39(3): 55−67. doi: 10.3969/j.issn.0253-4193.2017.03.005
[7]	Guo Chao, He Qing, Guo Leicheng, et al. A study of in-situ sediment flocculation in the turbidity maxima of the Yangtze Estuary[J]. Estuarine, Coastal and Shelf Science, 2017, 191: 1−9. doi: 10.1016/j.ecss.2017.04.001
[8]	Li Wenjie, Wang Jie, Yang Shengfa, et al. Determining the existence of the fine sediment flocculation in the Three Gorges Reservoir[J]. Journal of Hydraulic Engineering, 2015, 141(2): 05014008. doi: 10.1061/(ASCE)HY.1943-7900.0000921
[9]	Gratiot N, Manning A J. An experimental investigation of floc characteristics in a diffusive turbulent flow[J]. Journal of Coastal Research, 2004, (S41): 105−113.
[10]	Zhang Ying, Ren Jie, Zhang Wenyan. Flocculation under the control of shear, concentration and stratification during tidal cycles[J]. Journal of Hydrology, 2020, 586: 124908. doi: 10.1016/j.jhydrol.2020.124908
[11]	Liu Jinliang, Liang Junhong, Xu Kehui, et al. Modeling sediment flocculation in langmuir turbulence[J]. Journal of Geophysical Research: Oceans, 2019, 124(11): 7883−7907. doi: 10.1029/2019JC015197
[12]	Markussen T N, Andersen T J. Flocculation and floc break-up related to tidally induced turbulent shear in a low-turbidity, microtidal estuary[J]. Journal of Sea Research, 2014, 89: 1−11. doi: 10.1016/j.seares.2014.02.001
[13]	Mikkelsen O A, Curran K J, Hill P S, et al. Entropy analysis of in situ particle size spectra[J]. Estuarine, Coastal and Shelf Science, 2007, 72(4): 615−625. doi: 10.1016/j.ecss.2006.11.027
[14]	Lee B J, Fettweis M, Toorman E, et al. Multimodality of a particle size distribution of cohesive suspended particulate matters in a coastal zone[J]. Journal of Geophysical Research: Oceans, 2012, 117(C3): C03014.
[15]	Lee B J, Toorman E, Fettweis M. Multimodal particle size distributions of fine-grained sediments: mathematical modeling and field investigation[J]. Ocean Dynamics, 2014, 64(3): 429−441. doi: 10.1007/s10236-014-0692-y
[16]	Huang Jie, Wang Simin, Li Xinran, et al. Effects of shear stress and salinity stratification on floc size distribution during the dry season in the Modaomen Estuary of the Pearl River[J]. Frontiers in Marine Science, 2022, 9: 836927. doi: 10.3389/fmars.2022.836927
[17]	Lasareva E V, Parfenova A M, Romankevich E A, et al. Organic matter and mineral interactions modulate flocculation across arctic river mixing zones[J]. Journal of Geophysical Research: Biogeosciences, 2019, 124(6): 1651−1664. doi: 10.1029/2019JG005026
[18]	Dyer K R, Manning A J. Observation of the size, settling velocity and effective density of flocs, and their fractal dimensions[J]. Journal of Sea Research, 1999, 41(1/2): 87−95.
[19]	Li Dongyi, Li Yunhai, XuYonghang. Observations of distribution and flocculation of suspended particulate matter in the Minjiang River Estuary, China[J]. Marine Geology, 2017, 387: 31−44. doi: 10.1016/j.margeo.2017.03.006
[20]	谢荣耀, 刘锋, 罗向欣, 等. 河控型河口盐度层化对悬沙的捕集机制——以洪季磨刀门河口为例[J]. 海洋学报, 2021, 43(5): 38−49. Xie Rongyao, Liu Feng, Luo Xiangxin, et al. Sediment trapping mechanism by salinity stratification in a river-dominted estuary: a case study of the Modaomen Estuary in flood season[J]. Haiyang Xuebao, 2021, 43(5): 38−49.
[21]	Zhang Ying, Ren Jie, Zhang Wenyan, et al. Importance of salinity-induced stratification on flocculation in tidal estuaries[J]. Journal of Hydrology, 2021, 596: 126063. doi: 10.1016/j.jhydrol.2021.126063
[22]	Liu Feng, Chen Hui, Cai Huayang, et al. Impacts of ENSO on multi-scale variations in sediment discharge from the Pearl River to the South China Sea[J]. Geomorphology, 2017, 293: 24−36. doi: 10.1016/j.geomorph.2017.05.007
[23]	Liu Feng, Yuan Lirong, Yang Qingshu, et al. Hydrological responses to the combined influence of diverse human activities in the Pearl River delta, China[J]. CATENA, 2014, 113: 41−55. doi: 10.1016/j.catena.2013.09.003
[24]	Tan Chao, Huang Bensheng, Liu Feng, et al. Recent morphological changes of the mouth bar in the Modaomen Estuary of the Pearl River Delta: causes and environmental implications[J]. Ocean & Coastal Management, 2019, 181: 104896.
[25]	Jia Liangwen, Wen Yi, Pan Shunqi, et al. Wave-current interaction in a river and wave dominant estuary: aseasonal contrast[J]. Applied Ocean Research, 2015, 52: 151−166. doi: 10.1016/j.apor.2015.06.004
[26]	贾良文, 吕晓莹, 程聪, 等. 珠江口磨刀门月际尺度地貌演变研究[J]. 海洋学报, 2018, 40(9): 65−77. doi: 10.3969/j.issn.0253-4193.2018.09.006 Jia Liangwen, Lü Xiaoying, Cheng Cong, et al. Study on the morphological evolution of the Modaomen Estuary in monthly scale[J]. Haiyang Xuebao, 2018, 40(9): 65−77. doi: 10.3969/j.issn.0253-4193.2018.09.006
[27]	卢陈, 吴尧, 杨裕桂, 等. 珠江磨刀门河口环流结构动力特征分析[J]. 海洋学报, 2022, 44(12): 9−18. Lu Chen, Wu Yao, Yang Yugui, et al. Characterizing the circulation flow structure in the Modaomen Estuary of the Zhujiang River[J]. Haiyang Xuebao, 2022, 44(12): 9−18.
[28]	Hussein T, dal Maso M, Petäjä T, et al. Evaluation of an automatic algorithm for fitting the particle number size distributions[J]. Boreal Environment Research, 2005, 10(5): 337−355.
[29]	Whitey K T. The physical characteristics of sulfur aerosols[J]. Atmospheric Environment, 2007, 41Suppl: 25−49.
[30]	Li Haiwei, Yang Qingshu, Mo Sihao, et al. Formation of turbidity maximum in the Modaomen Estuary of the Pearl River, China: the roles of mouth bar[J]. Journal of Geophysical Research: Oceans, 2022, 127(12): e2022JC018766. doi: 10.1029/2022JC018766
[31]	Stacey M T, Rippeth T P, Nash J D. Turbulence and stratification in estuaries and coastal seas[J]. Treatise on Estuarine and Coastal Science, 2011, 2: 9−35.
[32]	Geyer W R, MacCready P. The estuarine circulation[J]. Annual Review of Fluid Mechanics, 2014, 46: 175−197. doi: 10.1146/annurev-fluid-010313-141302
[33]	孙剑雄, 张文祥, 史本伟. 基于潮间带现场数据的底部切应力算法对比[J]. 海洋学研究, 2022, 40(1): 21−32. doi: 10.3969/j.issn.1001-909X.2022.01.003 Sun Jianxiong, Zhang Wenxiang, Shi Benwei, et al. Comparison of methods for calculating bottom shear stress based on intertidal flat field data[J]. Journal of Marine Sciences, 2022, 40(1): 21−32. doi: 10.3969/j.issn.1001-909X.2022.01.003
[34]	邹志利. 海岸动力学(第四版)[M]. 北京: 人民交通出版社, 2009: 94. Zou Zhili. Coastal hydrodynamics (4th edition)[M]. Beijing: China Communication Press, 2009: 94.
[35]	Miles J W. On the stability of heterogeneous shear flows[J]. Journal of Fluid Mechanics, 1961, 10(4): 496−508. doi: 10.1017/S0022112061000305
[36]	Byun J, Son M. On the relationship between turbulent motion and bimodal size distribution of suspended flocs[J]. Estuarine, Coastal and Shelf Science, 2020, 245: 106938. doi: 10.1016/j.ecss.2020.106938
[37]	Guo Chao, He Qing, van Prooijen B C, et al. Investigation of flocculation dynamics under changing hydrodynamic forcing on an intertidal mudflat[J]. Marine Geology, 2018, 395: 120−132. doi: 10.1016/j.margeo.2017.10.001