13 results on '"Ye, Leiping"'
Search Results
2. Impact of the Salt Concentration and Biophysical Cohesion on the Settling Behavior of Bentonites
- Author
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Krahl, Ellen, Vowinckel, Bernhard, Ye, Leiping, Hsu, Tian-Jian, and Manning, Andrew J.
- Subjects
ddc:627 ,bentonite -- suspension -- settling -- flocculation -- critical coagulation concentration -- extracellular polymeric substances ,ddc:6 ,General Earth and Planetary Sciences ,Veröffentlichung der TU Braunschweig ,ddc:62 ,Publikationsfonds der TU Braunschweig ,Article - Abstract
The flocculation behavior of clay minerals in aquatic environments is an important process in estuarine and riverine dynamics, where strong gradients in salinity can locally occur. Various contradicting observations have been reported in the literature on the impact of salt concentration on the settling process of cohesive sediments. To address this issue in a systematic manner, we investigate the settling behavior of clay minerals as a function of the salt concentration of the ambient water. Specifically, we focus on montmorillonite as a prototype clay mineral with a high cation exchange capacity (CEC). To this end, we study suspensions of Wyoming bentonite (Volclay SPV) as a very important constituent for many constructional and industrial purposes. We perform an experimental campaign to study the settling behavior of moderately turbid montmorillonite concentrations in monovalent salt solutions with different salinities (sodium chloride) to represent different environments ranging from deionized to ocean water, respectively. The subsequent settling process was monitored by taking pictures by a camera in regular time intervals over a total observation time up to 48 h. In addition, a modified hydrometer analysis is conducted to determine the grain size distribution (in terms of an equivalent diameter) of the flocculated clay suspension in salt water. Despite the rather high cation exchange capacity of the investigated clay (CEC=88.1), our results show that the settling speed drastically increases within a range of 0.6–1.0 PSU and stays approximately constant for higher salinities. This critical salt concentration is defined here as the critical coagulation concentration (CCC) and lies well below the salinity of natural open water bodies. The hydrometer analysis revealed that 60% of the agglomerates exceed the equivalent grain size of 20 μm. Finally, the findings of this study are supplemented with experiments studying the effect of Extracellular Polymeric Substances (EPS) on the flocculation behavior of bentonite in salt water. Our results demonstrate that salinity is the original trigger for flocculation, whereas EPS allows for even larger floc size but it does not play a significant role for the settling processes of bentonite in estuarine environments.
- Published
- 2022
3. Current- and Wave-Generated Bedforms on Mixed Sand–Clay Intertidal Flats: A New Bedform Phase Diagram and Implications for Bed Roughness and Preservation Potential
- Author
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Baas, Jaco H., Malarkey, Jonathan, Lichtman, Ian D., Amoudry, Laurent O., Thorne, Peter D., Hope, Julie A., Peakall, Jeffrey, Paterson, David M., Bass, Sarah J., Cooke, Richard D., Manning, Andrew J., Parsons, Daniel R., Ye, Leiping, Baas, Jaco H., Malarkey, Jonathan, Lichtman, Ian D., Amoudry, Laurent O., Thorne, Peter D., Hope, Julie A., Peakall, Jeffrey, Paterson, David M., Bass, Sarah J., Cooke, Richard D., Manning, Andrew J., Parsons, Daniel R., and Ye, Leiping
- Abstract
The effect of bedforms on frictional roughness felt by the overlying flow is crucial to the regional modelling of estuaries and coastal seas. Bedforms are also a key marker of palaeoenvironments. Experiments have shown that even modest biotic and abiotic cohesion in sand inhibits bedform formation, modifies bedform size, and slows bedform development, but this has rarely been tested in nature. The present study used a comprehensive dataset recorded over a complete spring–neap cycle on an intertidal flat to investigate bedform dynamics controlled by a wide range of wave and current conditions, including the effects of wave–current angle and bed cohesion. A detailed picture of different bedform types and their relationship to the flow, be they equilibrium, non-equilibrium, or relict, was produced, and captured in a phase diagram that integrates wave-dominated, current-dominated, and combined wave–current bedforms. This bedform phase diagram incorporates a substantially wider range of flow conditions than previous phase diagrams, including bedforms related to near-orthogonal wave–current angles, such as ladderback ripples. Comparison with laboratory-derived bedform phase diagrams indicates that washed-out ripples, lunate interference ripples and upper-stage plane beds replace the subaqueous dune field; such bedform distributions may be a key characteristic of intertidal flats. The field data also provide a means of predicting the dimensions of these bedforms, which can be transferred to other areas and grain sizes. We show that an equation for the prediction of equilibrium bedform size is sufficient to predict the roughness, even though the bedforms are highly variable in character and only in equilibrium with the flow for approximately half the time. Whilst the effect of cohesive clay is limited under more active spring conditions, clay does play a role in reducing the bedform dimensions under more quiescent neap conditions. We also investigated which combinations of
- Published
- 2021
4. The Role of Biophysical Stickiness on Oil-Mineral Flocculation and Settling in Seawater
- Author
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Ye, Leiping, primary, Manning, Andrew J., additional, Holyoke, James, additional, Penaloza-Giraldo, Jorge A., additional, and Hsu, Tian-Jian, additional
- Published
- 2021
- Full Text
- View/download PDF
5. Integrating field and laboratory approaches for ripple development in mixed sand–clay–EPS
- Author
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Baas, Jaco H., Baker, Megan L., Malarkey, Jonathan, Bass, Sarah J., Manning, Andrew J., Hope, Julie A., Peakall, Jeffrey, Lichtman, Ian D., Ye, Leiping, Davies, Alan G., Parsons, Daniel R., Paterson, David M., Thorne, Peter D., McArthur, Adam, Baas, Jaco H., Baker, Megan L., Malarkey, Jonathan, Bass, Sarah J., Manning, Andrew J., Hope, Julie A., Peakall, Jeffrey, Lichtman, Ian D., Ye, Leiping, Davies, Alan G., Parsons, Daniel R., Paterson, David M., Thorne, Peter D., and McArthur, Adam
- Abstract
The shape and size of sedimentary bedforms play a key role in the reconstruction of sedimentary processes in modern and ancient environments. Recent laboratory experiments have shown that bedforms in mixed sand–clay develop at a slower rate and often have smaller heights and wavelengths than equivalent bedforms in pure sand. This effect is generally attributed to cohesive forces that can be of physical origin, caused by electrostatic forces of attraction between clay minerals, and of biological origin, caused by ‘sticky’ extracellular polymeric substances (EPS) produced by micro‐organisms, such as microalgae (microphytobenthos) and bacteria. The present study demonstrates, for the first time, that these laboratory experiments are a suitable analogue for current ripples formed by tidal currents on a natural mixed sand–mud–EPS intertidal flat in a macrotidal estuary. Integrated hydrodynamic and bed morphological measurements, collected during a spring tide under weak wave conditions near Hilbre Island (Dee Estuary, north‐west England, UK), reveal a statistically significant decrease in current ripple wavelength for progressively higher bed mud and EPS contents, and a concurrent change from three‐dimensional linguoid to two‐dimensional straight‐crested ripple planform morphology. These results agree well with observations in laboratory flumes, but the rate of decrease of ripple wavelength as mud content increased was found to be substantially greater for the field than the laboratory. Since the formation of ripples under natural conditions is inherently more complex than in the laboratory, four additional factors that might affect current ripple development in estuaries, but which were not accounted for in laboratory experiments, were explored. These were current forcing, clay type, pore water salinity and bed EPS content. These data illustrate that clay type alone cannot explain the difference in the rate of decrease in ripple wavelength, because the bed clay contents
- Published
- 2019
6. Redefining ‘Clean’ Sand By Integrating Field And Laboratory Data On Mixed Sand–Clay–EPS Rippled-Bed Transport
- Author
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Baas, Jaco, Baker, Megan, Malarkey, Jonathan, Bass, Sarah, Manning, Andrew, Hope, Julie, Peakall, Jeffrey, Lichtman, Ian, Ye, Leiping, Davies, Alan, Parsons, Daniel, Paterson, David, and Thorne, Peter
- Subjects
bepress|Physical Sciences and Mathematics ,bepress|Physical Sciences and Mathematics|Earth Sciences|Sedimentology ,Earth Sciences ,Physical Sciences and Mathematics ,bepress|Physical Sciences and Mathematics|Earth Sciences ,Sedimentology ,EarthArXiv|Physical Sciences and Mathematics|Earth Sciences ,EarthArXiv|Physical Sciences and Mathematics|Earth Sciences|Sedimentology ,EarthArXiv|Physical Sciences and Mathematics - Abstract
The shape and size of sedimentary bedforms play a key role in the reconstruction of sedimentary processes in modern and ancient environments. Recent laboratory experiments have shown that bedforms in mixed sand–clay develop at a slower rate and often have smaller heights and lengths than equivalent bedforms in pure sand. This is generally attributed to cohesive forces that can be of physical origin, caused by electrostatic forces of attraction between clay minerals, and of biological origin, caused by ‘sticky’ extracellular polymeric substances (EPS) produced by micro-organisms, such as microalgae (microphytobenthos) and bacteria. In the present paper, we demonstrate, for the first time, that these laboratory experiments are a suitable analogue for current ripples formed by tidal currents on a natural mixed sand–mud–EPS intertidal flat in a macrotidal estuary. Moreover, both the field data and the laboratory data demonstrate that the widely used definitions of ‘clean sand’ (
- Published
- 2018
7. The role of biophysical cohesion on subaqueous bed form size
- Author
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Parsons, Daniel R., Schindler, Robert J., Hope, Julie A., Malarkey, Jonathan, Baas, Jaco H., Peakall, Jeffrey, Manning, Andrew J., Ye, Leiping, Simmons, Steve, Paterson, David M., Aspden, Rebecca J., Bass, Sarah J., Davies, Alan G., Lichtman, Ian D., Thorne, Peter D., NERC, University of St Andrews. School of Biology, University of St Andrews. Sediment Ecology Research Group, University of St Andrews. Marine Alliance for Science & Technology Scotland, University of St Andrews. Scottish Oceans Institute, and University of St Andrews. St Andrews Sustainability Institute
- Subjects
QH301 ,Biophysical ,QH301 Biology ,general [Geomorphology] ,Sediment ,Sediment transport ,Cohesivity ,Bed forms ,Roughness - Abstract
This work was supported by the UK Natural Environment Research Council under grant NE/I027223/1 (COHBED). D.M.P. acknowledges the support of the Marine Alliance for Science and Technology for Scotland (MASTS) pooling initiative in the completion of this study. MASTS is funded by the Scottish Funding Council (grant reference HR09011) and contributing institutions. Biologically active, fine-grained sediment forms abundant sedimentary deposits on Earth's surface, and mixed mud-sand dominates many coasts, deltas, and estuaries. Our predictions of sediment transport and bed roughness in these environments presently rely on empirically based bed form predictors that are based exclusively on biologically inactive cohesionless silt, sand, and gravel. This approach underpins many paleoenvironmental reconstructions of sedimentary successions, which rely on analysis of cross-stratification and bounding surfaces produced by migrating bed forms. Here we present controlled laboratory experiments that identify and quantify the influence of physical and biological cohesion on equilibrium bed form morphology. The results show the profound influence of biological cohesion on bed form size and identify how cohesive bonding mechanisms in different sediment mixtures govern the relationships. The findings highlight that existing bed form predictors require reformulation for combined biophysical cohesive effects in order to improve morphodynamic model predictions and to enhance the interpretations of these environments in the geological record. Publisher PDF
- Published
- 2016
8. The pervasive role of biological cohesion in bedform development
- Author
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Malarkey, Jonathan, Baas, Jaco H., Hope, Julie A., Aspden, Rebecca J., Parsons, Daniel R., Peakall, Jeff, Paterson, David M., Schindler, Robert J., Ye, Leiping, Lichtman, Ian D., Bass, Sarah J., Davies, Alan G., Manning, Andrew J., Thorne, Peter D., Malarkey, Jonathan, Baas, Jaco H., Hope, Julie A., Aspden, Rebecca J., Parsons, Daniel R., Peakall, Jeff, Paterson, David M., Schindler, Robert J., Ye, Leiping, Lichtman, Ian D., Bass, Sarah J., Davies, Alan G., Manning, Andrew J., and Thorne, Peter D.
- Abstract
Sediment fluxes in aquatic environments are crucially dependent on bedform dynamics. However, sediment-flux predictions rely almost completely on clean-sand studies, despite most environments being composed of mixtures of non-cohesive sands, physically cohesive muds and biologically cohesive extracellular polymeric substances (EPS) generated by microorganisms. EPS associated with surficial biofilms are known to stabilize sediment and increase erosion thresholds. Here we present experimental data showing that the pervasive distribution of low levels of EPS throughout the sediment, rather than the high surficial levels of EPS in biofilms, is the key control on bedform dynamics. The development time for bedforms increases by up to two orders of magnitude for extremely small quantities of pervasively distributed EPS. This effect is far stronger than for physical cohesion, because EPS inhibit sand grains from moving independently. The results highlight that present bedform predictors are overly simplistic, and the associated sediment transport processes require re-assessment for the influence of EPS.
- Published
- 2015
9. Sticky stuff: Redefining bedform prediction in modern and ancient environments
- Author
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Schindler, Robert J., primary, Parsons, Daniel R., additional, Ye, Leiping, additional, Hope, Julie A., additional, Baas, Jaco H., additional, Peakall, Jeff, additional, Manning, Andrew J., additional, Aspden, Rebecca J., additional, Malarkey, Jonathan, additional, Simmons, Steve, additional, Paterson, David M., additional, Lichtman, Ian D., additional, Davies, Alan G., additional, Thorne, Peter D., additional, and Bass, Sarah J., additional
- Published
- 2015
- Full Text
- View/download PDF
10. The pervasive role of biological cohesion in bedform development
- Author
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Malarkey, Jonathan, primary, Baas, Jaco H., additional, Hope, Julie A., additional, Aspden, Rebecca J., additional, Parsons, Daniel R., additional, Peakall, Jeff, additional, Paterson, David M., additional, Schindler, Robert J., additional, Ye, Leiping, additional, Lichtman, Ian D., additional, Bass, Sarah J., additional, Davies, Alan G., additional, Manning, Andrew J., additional, and Thorne, Peter D., additional
- Published
- 2015
- Full Text
- View/download PDF
11. Physics of Cohesive Sediment Flocculation and Transport : State-of-the-Art Experimental and Numerical Techniques
- Author
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Vowinckel, Bernhard, Manning, Andrew J., Bai, Bofeng, Zhao, Kunpeng, Ye, Leiping, Meiburg, Eckart, and Hsu, Tian-Jian
- Subjects
Science / Earth Sciences - Abstract
Due to climate change, sea level rise and anthropogenic development, coastal communities have been facing increasing threats from flooding, land loss, and deterioration of water quality, to name just a few. Most of these pressing problems are directly or indirectly associated with the transport of cohesive fine-grained sediments that form porous aggregates of particles, called flocs. Through their complex structures, flocs are vehicles for the transport of organic carbon, nutrients, and contaminants. Most coastal/estuarine models neglect the flocculation process, which poses a considerable limitation of their predictive capability. We describe a set of experimental and numerical tools that represent the state-of-the-art and can, if combined properly, yield answers to many of the aforementioned issues. In particular, we cover floc measurement techniques and strategies for grain-resolving simulations that can be used as an accurate and efficient means to generate highly-resolved data under idealized conditions. These data feed into continuum models in terms of population balance equations to describe the temporal evolution of flocs. The combined approach allows for a comprehensive investigation across the scales of individual particles, turbulence and the bottom boundary layer to gain a better understanding of the fundamental dynamics of flocculation and their impact on fine-grained sediment transport.
- Published
- 2019
12. Oil-Mineral Flocculation and Settling Dynamics
- Author
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Manning, Andrew J., Ye, Leiping, Hsu, Tian-Jian, Holyoke, James, and Penaloza-Giraldo, Jorge A.
- Subjects
Science / Earth Sciences - Abstract
In recent decades, oil spill contamination has tended to occur more commonly in deltaic and estuarial systems. The management of oil spillages has been a major challenge in the surrounding deltas due to the highly sensitivity nature of deltaic ecosystems. Many deltas have an abundance of clay minerals that can flocculate, and these play an important role in determining the transport of spilled oil contamination and its eventual fate, particularly given that suspended sediment and microbial activities are often prevalent and diverse in natural environments. The primary work presented here focuses on laboratory experimental studies that help develop improved parameterizations of flocculation processes for oil-sediment-biogeochemical modeling. Oil-mineral flocs (OMA) have been successfully created from a series of laboratory flocculation experiments. A floc video instrument LabSFLOC-2 has been adopted for the first time to study the settling dynamics of OMAs. Experimental results reveal OMAs can easily form in any oil, cohesive sediment, and seawater mixtures. However, Kaolin and Bentonite forms dramatically different OMA structures, which leads to their variable characteristics. In the Bentonite clay cases, the oil flocs tend to be much larger and with higher densities than those in Kaolin clay cases, resulting in significant variability of flocs settling velocities.
- Published
- 2019
13. The role of biophysical cohesion on subaqueous bed form size.
- Author
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Parsons DR, Schindler RJ, Hope JA, Malarkey J, Baas JH, Peakall J, Manning AJ, Ye L, Simmons S, Paterson DM, Aspden RJ, Bass SJ, Davies AG, Lichtman ID, and Thorne PD
- Abstract
Biologically active, fine-grained sediment forms abundant sedimentary deposits on Earth's surface, and mixed mud-sand dominates many coasts, deltas, and estuaries. Our predictions of sediment transport and bed roughness in these environments presently rely on empirically based bed form predictors that are based exclusively on biologically inactive cohesionless silt, sand, and gravel. This approach underpins many paleoenvironmental reconstructions of sedimentary successions, which rely on analysis of cross-stratification and bounding surfaces produced by migrating bed forms. Here we present controlled laboratory experiments that identify and quantify the influence of physical and biological cohesion on equilibrium bed form morphology. The results show the profound influence of biological cohesion on bed form size and identify how cohesive bonding mechanisms in different sediment mixtures govern the relationships. The findings highlight that existing bed form predictors require reformulation for combined biophysical cohesive effects in order to improve morphodynamic model predictions and to enhance the interpretations of these environments in the geological record.
- Published
- 2016
- Full Text
- View/download PDF
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