A study of in-situ sediment flocculation in the turbidity maxima of the Yangtze Estuary

Guo, Chao; He, Qing; Guo, Leicheng; Winterwerp, Johan C.

doi:10.1016/j.ecss.2017.04.001

Cited by 66 publications

(47 citation statements)

References 48 publications

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“…Our measurements are consistent with the ones they reported in their Figure 1 and are compatible with a general trend of a decrease in ∆ρ f with increasing D 50 [83][84][85][86][87][88]. However, we must note that most of the diameters considered in Khelifa & Hill'study were deduced from image analysis and many values were much higher than the limit imposed by the LISST measurement range.…”

Section: And Excess Of Density Of Flocssupporting

confidence: 92%

“…Its upper part is well mixed until salinity around 1 psu, then its downstream part is stratified. The range of salinity values at which we observed ETMs from less than 1 psu tõ 15 psu is consistent with other ETMs described in the literature by [16,84]. Two main origins have been proposed to explain the formation of Turbidity Maximum in estuaries.…”

Section: On the Origins Of Etms In The Cam-nam Trieu Estuarysupporting

confidence: 78%

“…Fettweis [68] reported that the floc fractal dimension calculated from in situ measurements varied typically from 1.6 to 2.3 and that uncertainties remain on its accuracy. In wet season in the Yangtze Estuary, Guo et al [84] reported d f values varying between 1.5 and 2.1 (around a best fit = 1.8). Based on measurements in the Seine estuary, Verney et al [89] reported d f values between 1.62 and 1.82, with a mean of 1.75.…”

Section: Fractal Dimensionmentioning

confidence: 99%

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Estuarine Turbidity Maxima and Variations of Aggregate Parameters in the Cam-Nam Trieu Estuary, North Vietnam, in Early Wet Season

Vinh¹,

Ouillon

2018

Water

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Abstract:This study aims at exploring the characteristic parameters of the Estuarine Turbidity Maxima (ETM) and at investigating their tidal variations within the Cam-Nam Trieu estuary (North Vietnam) during the early wet season. Six longitudinal river transects were performed at spring tide. Two types of ETM were observed: an upper well mixed ETM with high Suspended Particulate Matter (SPM) concentrations up to the surface at low salinity (0.11 to <1 psu), and a lower ETM confined in a bottom layer over stratified waters at salinities between~1 psu and 15 psu. Their length depended on the longitudinal salinity gradient and was highest at low tide than at high tide. D 50 of the flocs varied between 35 and 90 µm, their excess of density between 60 and 300 kg m −3 and their settling velocity ranged from 0.07 to 0.55 mm s −1 with values between 0.12 and 0.40 mm s −1 in the core of ETMs. The average fractal dimension of flocs was estimated to vary between 1.93 (at high tide) to 2.04 (at low tide).

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Section: And Excess Of Density Of Flocssupporting

confidence: 92%

Section: On the Origins Of Etms In The Cam-nam Trieu Estuarysupporting

confidence: 78%

Section: Fractal Dimensionmentioning

confidence: 99%

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Estuarine Turbidity Maxima and Variations of Aggregate Parameters in the Cam-Nam Trieu Estuary, North Vietnam, in Early Wet Season

Vinh¹,

Ouillon

2018

Water

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“…The cross‐shoal flow over Jiuduan Shoal (Figure b) generates a strong northward lateral flow with an amplitude up to 0.2 m/s, which is far greater than that in single‐channel estuaries (Zhu et al, ). The turbidity maximum zone, formed under the combined influence of estuarine circulation (Liu et al, ), sediment flocculation (Guo et al, ), and tidal asymmetry (Li et al, ), is located in the North Channel, North Passage, and South Passage. Water depth is shoal in these channels with an averaged depth of 7 m due to sediment accumulation (Chen et al, ).…”

Section: Study Sitementioning

confidence: 99%

Response of Stratification Processes to Tidal Current Alteration due to Channel Narrowing and Deepening

Zhu

Shen

2020

JGR Oceans

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Stratification in estuaries has received much focus due to its importance in estuarine hydrodynamics and material transport. By utilizing a well‐calibrated numerical model, in this work we investigate the changes in stratification in the deepened and narrowed North Passage of the Changjiang Estuary. Before channel narrowing and deepening, lateral straining, generated by the interaction between vertical shear in lateral flow and transverse salinity gradient, is the dominant factor that controls stratification. A two‐layer structure of the lateral flow strains the isopycnal transversely, resulting in rapid stratification from late flood to early ebb tide. Thus, maximum stratification occurs during the early ebb. Then, the stratification was suppressed by the vertical mixing and the less stratified water advected from upstream, even the vertical shear in along‐channel flow continued to strain the isopycnal. After channel deepening and narrowing, the salinity in the upper water column experienced a sharp vertical gradient during the entire tidal cycle, while the transverse salinity gradient and lateral flow are profoundly reduced. The impact of lateral straining on stratification becomes minor. The enhanced stratification results in a sharp decrease in turbulent mixing within the pycnocline. The water movement in the upper layer is in a free‐stream status and the tidal current speed increases significantly. The alteration of the vertical current structure enhances the along‐channel tidal straining and stratification is most vigorous on late ebb tide.

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“…In this study, attention is given to the substrates of cohesive particles (clay and silt), which have significant impacts on both engineering issues such as channel siltation (e.g., Fettweis et al, 2016;Guo et al, 2017;Song & Wang, 2013) and ecological issues such as contaminant transport (e.g., Cheng et al, 2015;Droppo et al, 2016;Li et al, 2017). Previous work has largely focused on biofilm effects on sediment stability and erodibility (e.g., Chen et al, 2017;Droppo et al, 2016); nevertheless, biofilms in suspended sediment particles also have considerable influence on fine sediment aggregation in coastal and estuarine environments.…”

Section: Introductionmentioning

confidence: 99%

An Approach to Modeling Biofilm Growth During the Flocculation of Suspended Cohesive Sediments

et al. 2019

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The floc size distribution (FSD) is crucial to predict cohesive sediment dynamics in aquatic environments. Recently, increasing attention has been given to biofilm effects on the FSDs of suspended particles since the presence of biofilms on particle surfaces may lead to larger flocs and thus higher settling velocities. In this study, results from a settling column experiment conducted by Tang and Maggi (2018; https://doi.org/10.1002/2017JG004165) under nutrient‐free and biomass‐free, nutrient‐affected and biomass‐free, and nutrient‐affected and biomass‐affected conditions, with different suspended sediment concentrations, shear rates, and nutrient concentrations, have been used to validate modeled FSDs that is based on the population balance equation solved by the quadrature method of moments. In addition to the processes of aggregation and breakage, the effects of biofilm are expressed in the growth term of the population balance equation. The logistic growth pattern is used to account for an increase in biomass, which is primarily controlled by the specific growth rate and the carrying capacity. In this study, the biofilm growth rate is assumed nutrient dependent, and the carrying capacity of floc size is hypothesized to be proportional to the Kolmogorov microscale. With eight size classes to interpret a simulated FSD, the predicted and observed FSDs exhibit a reasonable match for all nutrient‐free and biomass‐free, nutrient‐affected and biomass‐free, and nutrient‐affected and biomass‐affected conditions. This simplified bioflocculation model fills the gap between the simulations of the FSDs of cohesive sediments without and with biofilms and has the potential to be included in large‐scale models in the future.

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A study of in-situ sediment flocculation in the turbidity maxima of the Yangtze Estuary

Cited by 66 publications

References 48 publications

Estuarine Turbidity Maxima and Variations of Aggregate Parameters in the Cam-Nam Trieu Estuary, North Vietnam, in Early Wet Season

Estuarine Turbidity Maxima and Variations of Aggregate Parameters in the Cam-Nam Trieu Estuary, North Vietnam, in Early Wet Season

Response of Stratification Processes to Tidal Current Alteration due to Channel Narrowing and Deepening

An Approach to Modeling Biofilm Growth During the Flocculation of Suspended Cohesive Sediments

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