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The levels of dissolved sulfate and methane are crucial indicators in the geochemical analysis of pore water. Compositional analysis of pore water samples obtained from sea trials was conducted using Raman spectroscopy. It was found that the concentration of SO42- in pore water samples decreases as the depth increases, while the expected Raman sign...
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... 4 is immiscible with water. Thus, the trace CH 4 dissolved in water is enriched into CCl 4 after the extraction. Then, the CCl 4 after extraction is taken as samples for Raman spectrum acquisition. The molecular density of CH 4 ( C in Equation (1)) in CCl 4 is much bigger than that in H 2 O. Finally, the Raman spectrum of CCl 4 after the extraction acquired by the conventional experimental setup with an integration time of 0.1 s, which is an average result of ten measurements, is shown in Figure 9. The Raman peak of methane is located at 2907 cm and can be clearly observed in Figure 9. This indicates that, after the extraction, the methane dissolved in water is enriched into the CCl 4 . The preliminary result shows that the methane dissolved in water with concentration below 1.14 mmol/L could be indirectly detected assisted by CCl 4 extraction. There are still many opportunities for optimizing this approach, and there is a long way to go in order to achieve a quantitative analysis of methane dissolved in water. For the compositional analysis of pore water, Raman spectra of the pore water samples obtained from the sea trials were acquired. According to the linear function obtained from the calibration curve, the concentration of SO 42 − in pore water is inversely calculated according to the linear function obtained from the calibration curve. It is found that the concentration of SO 42 − in pore water samples decreases as the depth increases. However, methane cannot be detected using Raman spectroscopy because of its low concentration. Two approaches are proposed and used for a better analysis of pore water samples. One approach uses a LCOF as a sample container to enlarge the optical path length for detection of SO 42 − . The other approach is an enrichment process for methane with CCl 4 extraction. With the assistance of a LCOF whose physical length is 50 cm, the LOD of Raman spectroscopy is significantly improved, and the Raman signal of SO 42 − is amplified over 10 times compared to that obtained with a conventional Raman experimental setup. By the means of extraction, the trace methane dissolved in water is enriched into CCl 4 because the solubility of methane in water and CCl 4 differs immensely. Hence ...
Context 2
... 4 is immiscible with water. Thus, the trace CH 4 dissolved in water is enriched into CCl 4 after the extraction. Then, the CCl 4 after extraction is taken as samples for Raman spectrum acquisition. The molecular density of CH 4 ( C in Equation (1)) in CCl 4 is much bigger than that in H 2 O. Finally, the Raman spectrum of CCl 4 after the extraction acquired by the conventional experimental setup with an integration time of 0.1 s, which is an average result of ten measurements, is shown in Figure 9. The Raman peak of methane is located at 2907 cm and can be clearly observed in Figure 9. This indicates that, after the extraction, the methane dissolved in water is enriched into the CCl 4 . The preliminary result shows that the methane dissolved in water with concentration below 1.14 mmol/L could be indirectly detected assisted by CCl 4 extraction. There are still many opportunities for optimizing this approach, and there is a long way to go in order to achieve a quantitative analysis of methane dissolved in water. For the compositional analysis of pore water, Raman spectra of the pore water samples obtained from the sea trials were acquired. According to the linear function obtained from the calibration curve, the concentration of SO 42 − in pore water is inversely calculated according to the linear function obtained from the calibration curve. It is found that the concentration of SO 42 − in pore water samples decreases as the depth increases. However, methane cannot be detected using Raman spectroscopy because of its low concentration. Two approaches are proposed and used for a better analysis of pore water samples. One approach uses a LCOF as a sample container to enlarge the optical path length for detection of SO 42 − . The other approach is an enrichment process for methane with CCl 4 extraction. With the assistance of a LCOF whose physical length is 50 cm, the LOD of Raman spectroscopy is significantly improved, and the Raman signal of SO 42 − is amplified over 10 times compared to that obtained with a conventional Raman experimental setup. By the means of extraction, the trace methane dissolved in water is enriched into CCl 4 because the solubility of methane in water and CCl 4 differs immensely. Hence ...
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Abstract The effective radiative forcing (ERF) of anthropogenic gases and aerosols under present-day conditions relative to preindustrial conditions is estimated using the Meteorological Research Institute Earth System Model version 2.0 (MRI-ESM2.0) as part of the Radiative Forcing Model Intercomparison Project (RFMIP) and Aerosol and Chemistry Mod...
Citations
... In the aerobic sedimentary environment, the Permian Chihsian Formation in South China has deposited a wide range of carbonate and bioclastic, in which aragonite and organic matter accounted for a significant proportion (Sandberg, 1983;Yan and Wu, 2006). A large amount of sulfate, the main sulfur compound in seawater, could be preserved in pore water with no reduction (Du et al., 2015). Dissolved oxygen oxidized organic matter and led to the release of CO 2 (R1) (Fig. 9a). ...
... For the experiment, magnetic particle-coated 8.47µm size polystyrene microplastics were utilized (Iri et al. 2021). Firstly the Raman signal of 2 ml of deionized water was recorded as a reference measurement which possesses a peak at 1600 cm −1 wavenumber (Du et al. 2015); then, a tiny amount of microplastics was added to the cuvette with particle concentration from 0.03% to 0.075% w/v. Raman spectra were collected at wavenumbers between 3000 and 3500 cm −1 . ...
The rise of microplastic waste is an alarming issue and poses a worldwide environmental threat. Due to their shapes, sizes, translucency or transparency, surface structure, and atmospheric conditions, in situ identification of these small particles is challenging. This review paper compiles various sensors like autonomous sensors, optical sensors, resonance sensors, biosensor, etc., developed and available for detecting microplastics in environmental reservoirs. Majority of these sensors have done a feasibility study for microplastics detection using artificially created samples of nylon, translucent LDPE (low-density polyethylene), PET (polyethylene terephthalate), PVC (polyvinyl chloride), PS (polystyrene).
... semiconductor methane sensor with external semipermeable membrane, membrane support, semiconductor part, electronic part and connector, reproduced from [62] with permission from Springer, 2014. (c) Experimental setup of the system based on Raman spectroscopy with liquid-core optical fiber (LCOF) to measure methane dissolved in water, reproduced from [63] with permission from MDPI, 2015. (d) High-pressure test system of fiber refractometer for detecting methane in deep ocean, reproduced from [64] with permission from Elsevier Sci. Ltd., 2014. ...
... In situ sensors can achieve real-time monitoring of dissolved methane, such as the electrochemical conductivity sensors based on semiconductor gas sensing materials [62,69], the optical sensors based on infrared absorption spectroscopy [70], Raman spectra [63] and mass spectrometry sensors [67]. Among them, electrochemical conductivity and off-axis integrated-cavity-output-spectroscopy sensing methods are commercially available. ...
... In addition, many novel optical methane sensors have been reported recently. Du et al. proposed a method based on Raman spectroscopy to measure methane dissolved in water ( Figure 2c) [63]. The device is based on liquid-core optical fiber (LCOF) with diode-pumped solid-state laser as the light source, which successfully detects the enrichment process of methane dissolved in water with a detection limit of below 1.14 mM. ...
The exploration of the ocean is essential for the exploitation of marine resources and the sustainable development of human society. In order to assess both the health and the resources of the marine environment, a variety of chemical and biological sampling is needed. Traditionally, marine samples are collected on site and transported to a laboratory for analysis. Analytical methods are often tedious, and it is difficult to know the in situ real-time status. This review provides a comprehensive summary of the development of in situ chemical and biological sensors for the typical compounds in the ocean, including methane, radon, ferrous ion, carbon dioxide, microorganisms, pollutants, nutrients and seafood. Different types of sensors for each compound are highlighted, such as novel electrochemical and optical sensors. Commercial status of different sensors is introduced, and performance of representative sensors is compared and discussed deeply. The advantages and disadvantages of each sensing technique are analyzed and evaluated in detail. Finally, future prospects and work directions are presented, such as the deployment of these in situ sensors on fixed and/or moving platforms, development of microfluidic sensors and exploration of new antifouling materials and methods. This paper could serve as a resource for developing more advanced in situ chemical sensors and biosensors for marine scientific research, as well as related practical applications for monitoring marine resource exploration and exploitation and for environmental protection.
... Two bands are at 521 and 745 cm −1 which can be identified as for B 5 O 6 (OH) − 4 and B(OH) − 4 molecules, respectively [64,65]. The other detected bands are at 1646 cm −1 which relates to water [71][72][73]. Bands at 930 cm −1 (NBA solutions) or 960 cm −1 (EBA solutions) also show up, possibly related to B-O bands in complicated heavy molecules containing boron and sodium atoms [74,75]. ...
Boric acid is a significant radioactive waste generated during the operation of nuclear power plants. Cementitious materials have been widely studied for the immobilization of boric acid. The generally used natural boric acid has been replaced by enriched boric acid for geochemical reasons and are expected to have varied behaviors in cementitious matrices. Results showed that simulated enriched/natural boric acid liquid wastes mostly contain boron in $${\mathrm{B}(\mathrm{OH})}_{4}^{-}$$ B ( OH ) 4 - and $${{\mathrm{B}}_{5}{\mathrm{O}}_{6}(\mathrm{OH})}_{4}^{-}$$ B 5 O 6 ( OH ) 4 - ionic forms, but the mass ratio of these species is higher in enriched boric acid solutions. In function with the concentration of enriched/natural boric acid, the solidified cementitious materials show different mineralogy.
... The Raman peak of the KBrO 3 band coincides well with those observed in the Raman spectrum of KBrO 3 . However, after stirring, the Raman spectra showed that the carbon band disappeared, KBrO 3 decreased, and that its band became wide; in addition, new five bands located at 148 cm −1 , 393.8 cm −1 , 547.4 cm −1 , 633.4 cm −1 , and 1091 cm −1 , attributed to TiO 2 and SO 2− 4 , were observed [39,40]. The observation confirms that SO 4 components precipitated during the photodegradation process and carbon flitted in the solution due to its small weight compared to the SO 4 complexes. ...
In this study, the enhanced photodegradation of a high-concentration phenol red (PR) using very fine TiO2 nanocrystals by adding a KBrO3 electron acceptor was reported for the first time. The structural study on TiO2 nanocrystals using HRTEM, XRD, Raman, and EDX was performed and it confirmed the anatase phase of TiO2 nanocrystals. UV–Vis absorbance of 20 mg.L−1 PR was measured and the photodegradation was extracted. The KBrO3 concentration effects exhibited an important enhancement in the degradation of PR dye. The efficiency of PR was increased during 110 min from 75% of pure TiO2 to 92% and 98% of TiO2 with 1 mg and 5 mg KBrO3, respectively. For different samples, a first-order kinetic of dye degradation is confirmed. The instantaneous amount of degraded dye increased from 150 to 180 and 197 mg/g TiO2 with 1 mg and 5 mg KBrO3, respectively. The mechanism of the photodegradation reaction confirms the effect of OH- radicals on increasing the photocatalytic activities. The addition of electron acceptors KBrO3 improved the photocatalysis rate, where it prevented e-h recombination through conduction band electron capture, which increases the concentration of hydroxyl radicals. The proposed mechanism and results were supported by photocurrent measurements and a Raman spectra analysis of the final photodegraded products. The photocurrent of TiO2 was observed at 1.2 µA, which was significantly improved up to 13.2, and 21.3 µA with the addition of 1 mg and 5 mg of KBrO3. The Raman spectra of the final products confirmed that SO42− and carbons are byproducts of PR degradation.
... We report here on marker-free and contactless measurements of concentrations by spatially resolved Raman and NMR spectroscopy in evaporating binary droplets. spectroscopy requires calibration through reference experiments (16)(17)(18). Both approaches allow the quantification of concentration gradients in sessile droplets, as is shown here. ...
... As described above the C-H stretching band of 1-hexanol (2,800 to 3,000 cm À1 ) and the C-D stretching band of 1-butanol-d 9 (2,000 to 2,400 cm À1 ) are baseline separated. Hence, the ratio of the integrated band intensities can be used as a measure for the concentration (29) by using a calibration curve (16)(17)(18). ...
Significance
Imagine you spill your drink and miss some spots when cleaning up. The next morning you notice that the stains look quite different on different surfaces. What has happened? In droplets of liquid mixtures, the components evaporate at different rates, which leads to gradients in concentration and surface tension. These gradients can cause, for example, so-called Marangoni flows, which in turn affect the evaporation process. To better understand evaporation-induced liquid flows, the concentration gradients have to be measured without disturbing the liquid. Marker molecules might be surface-active or even may affect the evaporation process. We report here on marker-free and contactless measurements of concentrations by spatially resolved Raman and NMR spectroscopy in evaporating binary droplets.
... However, electronics-based water monitoring systems have drawback such as limited water contaminants can be detected by sensors due to low sensitivity of electronic sensors when the contaminants are in low concentration. This results in low accuracy of data obtained [17,18]. ...
Water pollution is a detrimental issue that can affect health, economy, society, flora, and fauna. Monitoring water quality is important to mitigate water pollution issues. The purpose of this research is to investigate several water quality monitoring methods based on electronics and optical sensing. Electronics and optical sensing are among common and popular methods used to monitor water quality. The smart platform is used to work together with electronics and optical sensors to assist users in controlling the system. Both methods have their own benefit such as electronics sensing being portable and easy to handle whereas optical sensing does not affect the water sample, leading to higher accuracy results. Thus, the selection of the suitable method depends on the consumer’s requirement, cost, budget, and time.
... This was recorded as a reference measurement and by adding tiny amounts of microplastics, output data were recorded and analyzed. The spectrum of pure water depicted in Fig. 5(a) possesses a peak at the wavenumber~1600 cm −1 which we attribute to the signals received from the water molecules in agreement with Du et al. (2015). We would also expect to observe another peak at around 3400 cm −1 . ...
Unfortunately, the plastic pollution increases at an exponential rate and drastically endangers the marine ecosystem. According to World Health Organization (WHO), microplastics in drinking water have become a concern and may be a risk to human health. One of the major efforts to fight against this problem is developing easy-to-use, low-cost, portable microplastic detection systems. To address this issue, here, we present our prototype device based on an optical system that can help detect the microplastics in water. This system that costs less than $370 is essentially a low-cost Raman spectrometer. It includes a collimated laser (5 mW), a sample holder, a notch filter, a diffraction grating, and a CCD sensor all integrated in a 3D printed case. Our experiments show that our system is capable of detecting microplastics in water having a concentration less than 0.015% w/v. We believe that the designed portable device can find a widespread use all over the world to monitor the microplastic content in an easier and cost-effective manner.
... NMR is intrinsically calibration free, whereas Raman spectroscopy requires calibration through reference experiments. (14)(15)(16) Both approaches allow the quantification of concentration gradients in sessile droplets, as is shown here. ...
... Hence, the ratio of the integrated band intensities can be used as a measure for the concentration (27) by using a calibration curve. (14)(15)(16) The measurements show different evaporation behaviours for the two alcohols of different chain lengths. 1-Butanol and 1-butanol-d9 have lower boiling temperatures, higher vapor pressures and higher surface tensions -they evaporated within 30 min. ...
Understanding the evaporation process of binary sessile droplets is essential for optimizing various technical processes, such as inkjet printing or heat transfer. Liquid mixtures whose evaporation and wetting properties may differ significantly from those of pure liquids are particularly interesting. Concentration gradients may occur in these binary droplets. The challenge is to measure concentration gradients without affecting the evaporation process. Here, spectroscopic methods with spatial resolution can discriminate between the components of a liquid mixture. We show that confocal Raman microscopy and spatially resolved nuclear magnetic resonance (NMR) spectroscopy can be used as complementary methods to measure concentration gradients in evaporating 1-butanol/1-hexanol droplets on a hydrophobic surface. Deuterating one of the liquids allows analysis of the local composition through the comparison of the intensities of the CH and CD stretching bands in Raman spectra. Spatially resolved NMR spectroscopy is used to measure the composition at different positions of the droplet. Confocal Raman and spatially resolved NMR experiments show the presence of a vertical concentration gradient as the 1-butanol/1-hexanol droplet evaporates.
... They can detect the different concentrations of sulfate ions through the aggregation degree of gold nanoparticles [8] and the fluorescence intensity of a complex [9]. Raman spectroscopy has also been reported for the determination of sulfate ions dissolved in pore water of sediments [10], and it realized the diurnal variability change monitoring of the SO 4 2− intensity of offshore seawater [11]. Other techniques have been adopted to determine sulfate concentration, such as titration [12,13], atomic absorption spectroscopy (AAS) [14,15], ion chromatography (IC) [16,17], spectrophotometry [18], atomic fluorescence spectroscopy (AFS) [19], and inductively coupled plasma atomic emission spectroscopy (ICP-AES) [20,21]. ...
A new optical fiber sensor based on the fluorescence lifetime was prepared for specific detection of sulfate ion concentration, where 1,1′-(anthracene-9,10-diylbis(methylene))bis(3-(dodecylcarbamoyl)pyridin-1-ium) acted as the sulfate fluorescent probe. The probe was immobilized in a porous cellulose acetate membrane to form the sensitive membrane by the immersion precipitation method, and polyethylene glycol 400 acted as a porogen. The sensing principle was proven, as a sulfate ion could form a complex with the probe through a hydrogen bond, which led to structural changes and fluorescence for the probe. The signals of the fluorescence lifetime data were collected by the lock-in amplifier and converted into the phase delay to realize the detection of sulfate ions. Based on the phase-modulated fluorometry, the relationship between the phase delay of the probe and the sulfate ion concentration was described in the range from 2 to 10 mM. The specificity and response time of this optical fiber sensor were also researched.
