scholarly journals High frequency un-mixing of soil samples using a submerged spectrophotometer in a laboratory setting—implications for sediment fingerprinting

2021 ◽  
Author(s):  
Niels F. Lake ◽  
Núria Martínez-Carreras ◽  
Peter J. Shaw ◽  
Adrian L. Collins
Keyword(s):  
Particle Size ◽  
Soil Sample ◽  
Suspended Sediment ◽  
Temporal Frequency ◽  
Soil Samples ◽  
Sediment Sources ◽  
High Temporal Frequency ◽  
Novel Method ◽  
The Relationship

Abstract Purpose This study tests the feasibility of using a submersible spectrophotometer as a novel method to trace and apportion suspended sediment sources in situ and at high temporal frequency. Methods Laboratory experiments were designed to identify how absorbance at different wavelengths can be used to un-mix artificial mixtures of soil samples (i.e. sediment sources). The experiment consists of a tank containing 40 L of water, to which the soil samples and soil mixtures of known proportions were added in suspension. Absorbance measurements made using the submersible spectrophotometer were used to elucidate: (i) the effects of concentrations on absorbance, (ii) the relationship between absorbance and particle size and (iii) the linear additivity of absorbance as a prerequisite for un-mixing. Results The observed relationships between soil sample concentrations and absorbance in the ultraviolet visible (UV–VIS) wavelength range (200–730 nm) indicated that differences in absorbance patterns are caused by soil-specific properties and particle size. Absorbance was found to be linearly additive and could be used to predict the known soil sample proportions in mixtures using the MixSIAR Bayesian tracer mixing model. Model results indicate that dominant contributions to mixtures containing two and three soil samples could be predicted well, whilst accuracy for four-soil sample mixtures was lower (with respective mean absolute errors of 15.4%, 12.9% and 17.0%). Conclusion The results demonstrate the potential for using in situ submersible spectrophotometer sensors to trace suspended sediment sources at high temporal frequency.

Testing the ability of submersible spectrophotometers to trace suspended sediment sources at high-temporal frequency

2020 ◽  
Author(s):  
Niels Lake ◽  
Núria Martínez-Carreras ◽  
Peter Shaw ◽  
Adrian Collins
Keyword(s):  
Laboratory Experiment ◽  
Suspended Sediment ◽  
Suspended Particle ◽  
Temporal Frequency ◽  
Soil Samples ◽  
Mitigation Measures ◽  
High Temporal Resolution ◽  
Mechanical Stirring ◽  
High Temporal Frequency ◽  
Absorbance Spectra

<p>Reliable and detailed information on the primary sources of suspended sediment (SS) and sediment-associated nutrient and contaminant transfers is needed to target mitigation measures for delivering healthy ecosystems and meeting environmental policy objectives. To this end, the SS source fingerprinting approach is proven an effective tool for assembling reliable information on the sources of SS and SS-associated nutrients and contaminants within a catchment. However, SS source estimates at a high temporal resolution are often lacking due to the high workload and costs involved in collecting and analysing SS and soil samples using conventional means. Given this background, here, we propose the use of submersible spectrophotometers that measure absorbance spectra at 2.5 nm intervals in the 200-750 nm range (UV-VIS) in-situ and at high temporal frequency (i.e. minutes) to fingerprint SS sources. We hypothesise that increasing the measurement frequency will eventually help to better characterise changes in sources over time, whilst also giving further insights on how to improve the classical sediment fingerprinting approach, which is currently based on the use of temporally-lumped data. In this research, we first test our approach under fully controlled conditions in a laboratory experiment. To this end, we use a large cylindrical tank (40-L) equipped with a spectrophotometer as well as a LISST sensor (measuring the effective particle size distribution (PSD)). A mechanical stirring device ensures homogeneous conditions in the system and prevents the settling of soil particles (added in solution). The used soil samples originate from different areas within Luxembourg, whereby a selection was made based on differences in tracer properties and colour. The soils were sieved to three different fractions to take account of PSD control on tracer properties. Using the laboratory experiment, we investigated how suspended particle properties affect the absorbance spectra readings. In particular, we looked at the effects of: (i) increasing concentrations of suspended particles, and; (ii) differences in PSD. We then created artificial mixtures composed of two, three and four soil types mixed in different proportions to investigate if the absorbance readings at different wavelengths (i.e., considered as tracers or fingerprints) can be used to un-mix the known proportions of the SS sources. For this, we used the predictions of MixSIAR, a well-established Bayesian tracer un-mixing model. Our preliminary results indicate the promising use of high resolution absorbance data to un-mix artificial sediment mixtures. Ongoing work is testing the approach at larger scales.</p>

Multi-fractional sediment fingerprinting in monitoring sediment sources in a peri-urban Portuguese catchment

2021 ◽  
Author(s):  
Rory Walsh ◽  
Carla Ferreira ◽  
William Blake ◽  
Sam Higton ◽  
Antonio Ferreira
Keyword(s):  
Particle Size ◽  
Suspended Sediment ◽  
Agricultural Land ◽  
Size Fraction ◽  
Soil Samples ◽  
Sediment Fingerprinting ◽  
Bed Sediment ◽  
Sediment Sources ◽  
Geochemical Composition ◽  
Size Fractions

<p>This paper explores the potential for using multiple particle size fractions in a hierarchical geochemical sediment fingerprinting approach to the assessment of changes in sediment sources through time within a small Mediterranean peri-urban catchment. Conventional  sediment fingerprinting has focussed on the <63µm fraction of fine bed-sediment on the basis that this fraction represents suspended sediment, which in turn is considered dominant over bedload in catchment sediment budgets. In reality, however, coarser sediment than 63µm may form part of suspended sediment and/or occurs as relatively fast-moving fine bedload.  Furthermore, sediment sources vary in their particle size distribution and, as geochemical composition can vary with particle size, it is arguable that sediment fingerprinting studies should consider use of multiple size fractions.</p><p>This study explores this approach using <63µm, 63-125µm, 125-250 µm and 250-2000µm size fractions.  It focuses on the north-south flowing Ribeira dos Covões catchment (6.2 km<sup>2</sup>), on the outskirts of Coimbra in central Portugal. The climate is humid Mediterranean. Catchment geology is 56% sandstone (in the east), 41 % marly limestone (in the west) and 3 % alluvium. Current land-use is 56% woodland, 4 % agricultural and 40% urban (mainly residential, but also including a recently constructed enterprise park (5%) and major highway (1%)). Recent urbanization has largely occupied former agricultural land. </p><p>The study adopts a multi-proxy sediment fingerprinting approach to assessment of changes in sediment sources, based on geochemical (elemental) characterization of the four different size fractions of fluvial bed-sediment and soil samples, using a Niton x-ray fluorescence (XRF) elemental analyser. Sampling of fluvial sediment was carried out at 33 sites within the stream network (including all significant tributaries, downstream sites and the catchment outlet). Samples were collected in July 2018 and November 2018 following contrasting ‘late-wet-season’ and ‘end-of-dry-season’ events. In July 2018, samples of potential sediment sources were collected including: (i) soil surface (0-2cm) samples at 64 locations, (ii) 17 samples from eroding channel margin sites, and (iii) 15 samples of road sediment. All fluvial and soil samples were sieved to obtain the four target size fractions. The elemental geochemistry of each sample fraction at all fluvial and source sites was derived using the XRF analyser.  (These results were added to similar datasets previously obtained on three occasions in 2012-15 in a period of enhanced urban constructional disturbance). Differences (and similarities) in geochemical signatures between the different size fractions at each survey date at and between each tributary and potential source site were assessed using a range of statistical techniques.  Messages arising are discussed. For each size fraction and survey date, Bayesian unmixing models were used in a hierarchical (confluence-based) fashion to assess the contributions of sub-catchments to downstream sites and the catchment outlet. Modelling results for the two 2018 events were validated by comparing them with suspended sediment records collected at five tributary locations and at the catchment outlet.  Although overall, the modelling was successful in indicating and quantifying significant changes in sediment sources through time within the catchment, uncertainties in interpretation of the multiple fractions are identified and discussed. </p>

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>

High-frequency absorbance measurements for sediment source apportionment – laboratory and field assessment

2021 ◽  
Author(s):  
Niels Lake ◽  
Núria Martínez-Carreras ◽  
Peter Shaw ◽  
Adrian Collins
Keyword(s):  
Particle Size ◽  
Source Apportionment ◽  
High Frequency ◽  
Soil Samples ◽  
Sediment Source ◽  
Water Tank ◽  
Sediment Sources ◽  
Environmental Objectives ◽  
Set Up ◽  
Artificial Mixtures

<p>To manage effectively excessive sediment inputs to rivers and streams, it is crucial to have detailed and reliable information on key sediment sources. Such evidence is important for implementing targeted measures for improving ecosystem functioning and meeting environmental objectives. Although sediment fingerprinting is increasingly adopted worldwide to provide such evidence, current procedures do not provide detailed information on how sediment sources can change over both short (e.g., events and in between events) and long (e.g., over seasons or years) time scales. These limitations are mainly due to the conventional methods used for target sediment sampling and the high workloads and costs associated with laboratory analyses for tracers, which limit both high-frequency and longer duration sampling campaigns. To address this issue, we propose the use of a submersible spectrophotometer, which measures absorbance in the UV-VIS range in situ and at high frequency (e.g., minutes) to trace suspended sediment sources. In our proof of concept investigation, the approach was first tested in a laboratory setting, using soil samples and artificial mixtures with known proportions of two, three and four soil source samples in an experimental water tank. A total of six soil samples were collected, which were sieved to different fractions to investigate the influence of particle size on the sensor absorbance readings. Both soil samples and artificial mixtures were suspended in the laboratory tank set-up at different concentrations to investigate the effects on: (i) absorbance, and; (ii) un-mixing accuracy. The results showed that absorbance was linearly additive and could be used to predict dominant samples in the artificial mixtures correctly using a Bayesian tracer un-mixing model, largely regardless of particle size and of the concentration inside the experimental tank. This approach is currently being tested in a field experiment in the Attert River Basin (Luxembourg) to investigate if the results found in the laboratory experiments hold under natural field conditions. Our preliminary insights into the use of absorbance for sediment source apportionment in the field will be presented.</p>

scholarly journals Real-time cancer diagnosis of breast cancer using fluorescence lifetime endoscopy based on the pH

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jooran Lee ◽  
Byungyeon Kim ◽  
Byungjun Park ◽  
Youngjae Won ◽  
Sang-Yeob Kim ◽  
...  
Keyword(s):  
Real Time ◽  
Fluorescence Lifetime ◽  
Normal Tissues ◽  
Diagnosis Of Cancer ◽  
Novel Method ◽  
Hematoxylin And Eosin ◽  
Cancer Tissues ◽  
The Relationship

AbstractA biopsy is often performed for the diagnosis of cancer during a surgical operation. In addition, pathological biopsy is required to discriminate the margin between cancer tissues and normal tissues in surgical specimens. In this study, we presented a novel method for discriminating between tumor and normal tissues using fluorescence lifetime endoscopy (FLE). We demonstrated the relationship between the fluorescence lifetime and pH in fluorescein using the proposed fluorescence lifetime measurement system. We also showed that cancer could be diagnosed based on this relationship by assessing differences in pH based fluorescence lifetime between cancer and normal tissues using two different types of tumor such as breast tumors (MDA-MB-361) and skin tumors (A375), where cancer tissues have ranged in pH from 4.5 to 7.0 and normal tissues have ranged in pH from 7.0 to 7.4. To support this approach, we performed hematoxylin and eosin (H&E) staining test of normal and cancer tissues within a certain area. From these results, we showed the ability to diagnose a cancer using FLE technique, which were consistent with the diagnosis of a cancer with H&E staining test. In summary, the proposed pH-based FLE technique could provide a real time, in vivo, and in-situ clinical diagnostic method for the cancer surgical and could be presented as an alternative to biopsy procedures.

Meso Analysis on Soft Soil Uniaxial Consolidation Experiment with CT

2012 ◽  
Vol 204-208 ◽  
pp. 539-544
Author(s):  
Ling Tao Mao ◽  
Dan Zhao ◽  
Kai Zhou ◽  
Ze Xun Yuan ◽  
Ji Li An
Keyword(s):  
Soil Sample ◽  
Soft Soil ◽  
Ct Images ◽  
Soil Samples ◽  
Ct Image ◽  
Pressure Loading ◽  
Consolidation Process ◽  
Marine Deposits ◽  
Structure Changes ◽  
The Relationship

In this paper, marine sediments soft soil of Beigangchi wharf in Tianjin port was scanned by Computer Tomography(CT) in different load during uniaxial consolidation experiment. The CT images were analyzed to research on the relationship between the microcosmic characteristics of Marine deposits soil and it’s compression in Tianjin areas. The results show that: with the increase of the pressure loading, the average grey value of the CT images increases gradually, which illustrates that soil samples are compacted and the density increases. The variance decreasing of CT image grey value indicates that the soil sample get more evenly. Soft soil of Beigangchi wharf in Tianjin port has high compressibility through the changes of grey compression coefficient. This paper can be referenced for the research of the structure changes of the soil sample consolidation process.

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