A Generic Relation Between Turbidity, Suspended Particulate Matter Concentration, and Sediment Characteristics

Sehgal, Dhruv; Martínez‐Carreras, Núria; Hissler, Christophe; Bense, Victor; Hoitink, A.J.F.

doi:10.1029/2022jf006838

Cited by 8 publications

(8 citation statements)

References 79 publications

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“…Optical backscattering sensors were found to be suitable tools for sediment studies (e.g., Bowers et al., 2017; Druine et al., 2018). It is generally accepted that a linear regression between turbidity and SPM is acceptable, if the regression coefficient is >90% (Fettweis et al., 2019; Rasmussen et al., 2009; Sehgal et al., 2022). The regression line ( r = 0.98) between the optical turbidity and the filtered SPM Filter concentration (in mg l −1 ) has a slope of a = 1.1 and an intercept of b = 3.08.…”

Section: Methodsmentioning

confidence: 99%

From Particles to Flocs: Revealing Where Flocculation Occurs in the Nearfield of a Negatively‐Buoyant River Plume in a Large Lake (Lake Geneva)

Piton,

Lemmin,

Bourrin

et al. 2024

JGR Oceans

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The dynamics of sediments entering lakes in river plumes is virtually unknown. This field study provides unprecedented evidence of the initiation and evolution of suspended sediment flocculation in the nearfield of the negatively‐buoyant Rhône River plume, flowing as interflow in the thermocline of stratified Lake Geneva. Sediment floc property changes (formation, size, composition, shape) with depth and distance from the mouth, were determined by combining digital holographic camera LISST‐HOLO data with full‐depth in situ profiles of particle size (LISST‐100X), density, turbidity, currents and water samples taken along the plume path. The total suspended matter volume of inflowing Rhône River waters (∼155 mg l−1) mostly consisted of clays (<4 μm), very fine silts (4–8 μm) and small contributions of microflocs (20–100 μm). This composition was also found in the interflow plume core. Above the plume, in the epilimnion, fine silts, microflocs and numerous phytoplanktonic organisms (∼200 μm) were observed, representative of the lake background. High levels of shear (15–27 s−1) and turbulence occurred in the shear layer that formed between the interflow bottom and the hypolimnion below. It was found that macroflocs only formed in this shear layer. In the hypolimnion, sediment load was the lowest and macroflocs (up to ∼300 μm) composed of inorganic particles were dominant. The size of the largest flocs was limited by the size of the smallest turbulent eddies determined by the Kolmogorov microscale. Floc 3D fractal dimensions of ∼2.1–2.5 suggest an intermediate shape complexity between marine snow and sludge flocs.

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Section: Methodsmentioning

confidence: 99%

From Particles to Flocs: Revealing Where Flocculation Occurs in the Nearfield of a Negatively‐Buoyant River Plume in a Large Lake (Lake Geneva)

Piton,

Lemmin,

Bourrin

et al. 2024

JGR Oceans

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“…The additional in situ data from measurements at Everlange (Luxembourg) and Rotterdam (The Netherlands) were taken from Sehgal et al (2022c). The additional ex situ sources consist of two data sets: (a) measurements from several consecutive events sampled at Huncherange (Luxembourg), and (b) experimental data sets collected using a tank setup.…”

Section: Additional Data Setsmentioning

confidence: 99%

“…The script for the Monte Carlo bootstrap analysis, will be made available through the public repository of 4TU via de Lange (2023). The data for site Everlange and Rotterdam was taken from Sehgal et al (2022c). The data for site Huncherange and tank-setup was taken from Sehgal et al (2022d).…”

Section: Data Availability Statementmentioning

confidence: 99%

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The Impact of Flocculation on In Situ and Ex Situ Particle Size Measurements by Laser Diffraction

de Lange,

Sehgal,

Martínez‐Carreras

et al. 2023

Water Resources Research

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Accurate particle size distribution (PSD) measurements of suspended particulate matter (SPM) composed of flocs and aggregates are important to improve understanding of ecological and geomorphological processes, and for environmental engineering applications. PSDs can be measured in situ (in the field) using a submersible sensor, or ex situ (in the laboratory) using samples. The methodological choice is often guided by logistical factors, and the differences in PSDs acquired by in situ and ex situ measurements is of concern. In this study, a laser‐diffraction instrument (the LISST‐200X) was used to compare in situ and ex situ PSD measurements. Samples measured ex situ were stored for three consecutive weeks and measured each week in a laboratory using different stirrer speeds. We observed that ex situ measurements display a higher D50 (median particle size) than in situ measurements of the same sample (up to 613% larger, 112% on average). Our experiments show that the difference between in situ and ex situ measurements can be explained by flocculation of the riverine sediments during the first week of storage. During the subsequent ex situ measurements, the stirring results in a significantly lower D50. Ex situ measurements are therefore unsuitable for flocculated SPM. This study provides recommendations for optimizing PSD measurements by calculating the measurement times required to obtain robust PSD measurements (exceeding 3 min per sample), which are larger for field samples with coarser particles and wider PSDs.

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“…Other methods utilise RFID tags [8] but suffer from poor resolution and high power consumption. The most conventional method for measuring high turbid water flows are optical sensors due to their high accuracy [9], [10]. Despite their accuracy, these optical sensors require significant calibration to correct for particle size and density and cannot be used to measure high sediment concentrations due to sensor saturation [11].…”

Section: Introductionmentioning

confidence: 99%

Development of a Non-Cloggable Subsea Data Logger for Harsh Turbidity Current Monitoring

Bradley,

Ruffell,

Talling

et al. 2023

OCEANS 2023 - Limerick

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Large submarine flows of sediment (sand and mud), known as turbidity currents, transfer and bury significant amounts of organic carbon and pollutants to the deep sea via submarine canyons. They are also significant geohazards, regularly breaking networks of seabed telecommunications cables that carry > 99% of global data that underpin the internet. Despite this, key parameters (notably their sediment concentration) in these flows are yet to be directly measured in real-time due to their inherently harsh environment that is unsuitable for commercial conductivity sensors. To address this issue, a subsea datalogger (SSDL) is developed with a planar conductivity sensor head that can measure the sediment concentration within dense turbidity currents. Unlike conventional sensors, the planar design of the SSDL's sensor prevents clogging at high sediment concentrations, allowing for continuous measurements within turbidity currents. The conductivity sensor is developed with a temperature sensor which is measured using an external 16-Bit ADC which is controlled with a SAMD21 32-Bit ARM microcontroller. The SSDL measures the temperature and the conductivity of the seawater once every 4 seconds for over a year. In an initial device test, the SSDL can record a turbidity current within the Bute Inlet, Canada. It is found that the seawater's conductivity increases with salinity concentration and decreases with sediment concentration. The SSDL developed here can thus be used for both conventional subsea datalogging applications and high turbidity current applications.

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A Generic Relation Between Turbidity, Suspended Particulate Matter Concentration, and Sediment Characteristics

Cited by 8 publications

References 79 publications

From Particles to Flocs: Revealing Where Flocculation Occurs in the Nearfield of a Negatively‐Buoyant River Plume in a Large Lake (Lake Geneva)

From Particles to Flocs: Revealing Where Flocculation Occurs in the Nearfield of a Negatively‐Buoyant River Plume in a Large Lake (Lake Geneva)

The Impact of Flocculation on In Situ and Ex Situ Particle Size Measurements by Laser Diffraction

Development of a Non-Cloggable Subsea Data Logger for Harsh Turbidity Current Monitoring

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