Measurement in situ of the effective particle-size characteristics of fluvial suspended sediment by means of a field-portable laser backscatter probe: Some preliminary results

1995 ◽  
Vol 46 (1) ◽  
pp. 349 ◽  
Author(s):  
JM Phillips ◽  
DE Walling
Keyword(s):  
Particle Size ◽  
Suspended Sediment ◽  
Fluvial Systems ◽  
Hydrodynamic Behaviour ◽  
Geochemical Properties ◽  
Effective Particle Size ◽  
Particle Size Data ◽  
Effective Particle ◽  
Significant Spatial Variation

Sediment-associated transport frequently represents an important component of the flux of nutrients and contaminants through fluvial systems, and particle size exerts a fundamental influence upon the hydrodynamic behaviour and geochemical properties of the suspended sediment particles involved. Recent work has highlighted the need to distinguish between the ultimate and effective particle-size characteristics of fluvial suspended sediment. The latter may differ appreciably from the former owing to the existence of composite particles (aggregates or flocs). Obtaining representative data of the effective particle-size distribution ideally requires measurements to be made in situ. This paper describes the use of an immersible, portable laser backscatter probe (Par-Tec 200/300) to make measurements in situ of the effective particle-size characteristics of suspended sediment transported by the River Exe and its tributaries in Devon, UK. Within the study basin the effective and absolute particle-size characteristics of suspended sediment were documented at four sites. Significant spatial variation and inter- and intra-event temporal variation in the mean effective size are identified. The degree of aggregation is assessed by comparing the effective and absolute particle-size data. Such comparisons show aggregation to be an important process in the study basin, although its precise magnitude varies in both space and time.

Inferring suspended sediment carbon content and particle size at high frequency from the optical response of a submerged spectrometer 

2021 ◽  
Author(s):  
Dhruv Sehgal ◽  
Núria Martínez-Carreras ◽  
Christophe Hissler ◽  
Victor Bense ◽  
AJF (Ton) Hoitink
Keyword(s):  
Particle Size ◽  
Absorption Spectrum ◽  
Carbon Content ◽  
Suspended Sediment ◽  
High Frequency ◽  
Suspended Sediments ◽  
Ex Situ ◽  
Frequency Measurements ◽  
Component Form

<p>Manual and unattended sampling in the field and laboratory analysis are common practices to measure suspended sediment (SS) carbon content and particle size. However, one of the major drawbacks of these ex-situ methods is that they make high frequency measurements challenging. This includes restricted data collection due to limited access to the sampling locations during turbulent conditions or high flows, when the largest amount of sediments is transported downstream, introducing uncertainty in quantification of SS properties (particle size and carbon content) and sediment loads. Knowledge on SS carbon content and particle size is also important to better understand the multi-component form of suspended sediments (i.e. flocs) that directly affect sediment transport and other sediment properties (e.g. settling velocity and density). Moreover, SS carbon content and particle size exert an impact on the optical sensor readings that are traditionally used to measure turbidity. In that respect, high frequency measurements of SS carbon content and particle size could eventually help us to move from ‘local’ calibrations towards ‘global’ dependencies based on in-situ SS characterization.</p><p>In this study, we propose to use a submerged UV-VIS spectrometer to infer SS carbon content and particle size. The sensor measures the entire light absorption spectrum of water between 200 nm and 750 nm at sampling intervals as short as 2-minutes. To this end, we first test our approach under controlled conditions with an experimental laboratory setup consisting of a cylindrical tank (40-L) with an open top. An UV-VIS spectrometer and a LISST-200X sensor (to measure particle size distribution) are installed horizontally. A stirrer facilitates the homogeneous mixing of SS and prevents the settling of heavy particles at the bottom. We use the sediments sampled from 6 sites in Luxembourg with contrasting composition and representing different land use types and geological settings. The sampled sediments were wet sieved into 3 size classes to clearly recognize the effect of particle size on absorption. In our investigation, we use specific wavelengths, chemometric techniques and carbon content specific absorbance indices to infer SS composition and particle size from the absorption spectrum. Results are then validated using in-situ field data from two instrumented field sites in Luxembourg. Amid the challenge of associating laboratory and field results, the preliminary results indicate that the absorption spectrum measured with a submerged UV-VIS spectrometer can be used to estimate SS particle size and carbon content.</p>

Effects of Process Parameters on the Particle Size Distribution of Graphene Oxide Aqueous Dispersion

2013 ◽  
Vol 750-752 ◽  
pp. 1113-1116 ◽  
Author(s):  
Xue Bing Hu ◽  
Yun Yu ◽  
Jian Er Zhou ◽  
Li Xin Song
Keyword(s):  
Particle Size ◽  
Graphene Oxide ◽  
Particle Size Distribution ◽  
Size Distribution ◽  
Ultrasonic Treatment ◽  
Treatment Time ◽  
Aqueous Dispersion ◽  
Centrifugal Separation ◽  
Effective Particle Size ◽  
Effective Particle

During graphene oxide separation process, the effects of the process parameters such as centrifugal separation time and ultrasonic treatment time on the particle size distribution of graphene oxide aqueous dispersion were studied. The results show graphene oxide has the narrower particle size distribution and the smaller nominal effective particle size with increasing the centrifugal separation time from 20 min to 160 min. And there is a critical time in the ultrasonic treatment to obtain the narrower particle size distribution and smaller nominal effective particle size of graphene oxide. Graphene oxide has the narrower particle size distribution and the smaller nominal effective particle size when the ultrasonic treatment time is 4 h.

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