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[IEEE 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Huangshan, China (2019.8.5-2019.8.8)] 2019 18th International Conference on Optical Communications and Networks (ICOCN) - Quantitative Analysis of Heavy Metal Components in Soil by Laser-Induced Breakdown Spectroscopy Based on Principal Component Analysis
摘要： The calibration curves of heavy metal elements Cd and Ni were established based on laser induced breakdown spectroscopy of standard soil and soil to be tested. The plasma excitation test was carried out on the soil by laser induced breakdown spectroscopy to obtain a plasma spectrum with a wavelength of 300-1000 nm. By comparing the characteristic peaks in the obtained spectrum with the National Institute of Standards and Technology database, it is found that the test samples contain heavy metal elements such as Cd, Cr, Cu, Hg, Ni and W, and the Cd and the measured standard soil. The main method analysis of the peak of Ni element is carried out, and the principal component regression model is established to obtain the calibration curve of Cd and Ni elements, and then the content of Cd and Ni elements in the soil to be tested is estimated. Based on the concentration of the national standard soil sample and the measured spectral intensity, the linear correlation coefficients between the predicted and actual values of the Cd and Ni element contents were established to be 1 and 0.99443. Compared with the commonly used methods, laser-induced breakdown spectroscopy can quickly detect samples to be tested, and sample pretreatment is simple and less damage to the sample.
关键词： Principal component analysis,Soil heavy metal pollution,Laser induced breakdown spectroscopy,Qualitative and quantitative analysis
更新于2025-09-16 10:30:52
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Simultaneous Measurements of Soil CO and CH Fluxes Using Laser Absorption Spectroscopy
摘要： We present a method of simultaneously measuring soil CO2 and CH4 fluxes using a laser-based cavity ring-down spectrometer (CRDS) coupled to an automated non-steady-state chamber system. The differential equation describing the change in the greenhouse gas (GHG) mixing ratio in the chamber headspace following lid closure is solved for the condition when a small flow rate of chamber headspace air is pulled through the CRDS by an external pump and exhausted to the atmosphere. The small flow rate allows calculation of fluxes assuming linear relationships between the GHG mixing ratios and chamber lid closure times of a few minutes. We also calibrated the chambers for effective volume (Veff) and show that adsorption of the GHGs on the walls of the chamber caused Veff to be 7% higher than the geometric volume, with the near-surface soil porosity causing another 4% increase in Veff.
关键词： automated non-steady-state chamber system,soil CO2 and CH4 fluxes,laser absorption spectroscopy,cavity ring-down spectrometer
更新于2025-09-16 10:30:52
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Laser Diffraction Evaluation for Soil Particle Size Determination
摘要： Soil particle size distribution is a fundamental soil characteristic that highly affects soil water retention and soil fertility and microbial activity and requires accurate determination. The laser diffraction method is increasingly being applied to measure soil particle size because of its rapid processing, high reproducibility, and detailed analysis for a wide range of size fractions; yet some ambiguities exist regarding the comparability of its results with those obtained by other classical methods. In an article recently published in Soil Science Society of America Journal, researchers evaluate the laser diffraction method by comparing its particle size measurements on hundreds of soil samples collected from a typical cropland in the Beijing mountainous area with those determined by the standard sieve-pipette method and the absolute method of scanning electron microscopy. The team found that laser diffractometry significantly overestimated sand and silt but underestimated clay contents relative to the sieve-pipette method, resulting in soil textural class shifts in nearly half of the soil samples. However, significant linear regression models allow conversion of sand and silt contents between these two methods. In contrast to scanning electron microscopy, the laser diffraction method acquired dissimilar particle size distributions but statistically similar median particle sizes within the clay fraction. Results of this study demonstrate that the laser diffraction method is an effective tool for soil particle size analysis. Future work is needed to examine the applicability of this method in other regions with different soil types and clay mineralogy.
关键词： scanning electron microscopy,sieve-pipette method,soil particle size,laser diffraction
更新于2025-09-16 10:30:52
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Detection of heavy metal containment of soil pollution due to waste of paper industry using Nd:YAG laser induced breakdown spectroscopy
摘要： Detection of heavy metal containment of soil pollution has been made by using laser-induced breakdown spectroscopy (LIBS). A pulsed Nd:YAG laser (1064 nm, 8 ns, 200 mJ) was focused on to a soil sample, which is prepared in the form of pellet, at atmospheric pressure. Emission spectra taken from the waste-contaminated soil and uncontaminated soil were obtained. Plasma emissions are then detected using a multichannel analyzer (OMA) to obtain the emission line spectrum that represents the content of atoms and molecules in the target material. The spectrum is recorded and compared with the spectrum of reference standards of atoms, ions and molecules (National Institute of Standards and Technology/NIST) so that the atomic and molecular content in the sample can be known. From the results of the study it was found that there are elements of heavy metals in the form of Fe, Cd, and Mg in polluted soils.
关键词： LIBS,laser-induced breakdown spectroscopy,soil pollution,heavy metal,Nd:YAG laser
更新于2025-09-16 10:30:52
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A New Plant Indicator ( <i>Artemisia lavandulaefolia</i> DC.) of Mercury in Soil Developed by Fourier-Transform Near-Infrared Spectroscopy Coupled with Least Squares Support Vector Machine
摘要： A rapid indicator of mercury in soil using a plant (Artemisia lavandulaefolia DC., ALDC) commonly distributed in mercury mining area was established by fusion of Fourier-transform near-infrared (FT-NIR) spectroscopy coupled with least squares support vector machine (LS-SVM). The representative samples of ALDC (stem and leaf ) were gathered from the surrounding and distant areas of the mercury mines. As a reference method, the total mercury contents in soil and ALDC samples were determined by a direct mercury analyzer incorporating high-temperature decomposition, catalytic adsorption for impurity removal, amalgamation capture, and atomic absorption spectrometry (AAS). Based on the FT-NIR data of ALDC samples, LS-SVM models were established to distinguish mercury-contaminated and ordinary soil. The results of reference analysis showed that the mercury level of the areas surrounding mercury mines (0–3 kilometers, 7.52–88.59 mg/kg) was significantly higher than that of the areas distant from mercury mines (>5 kilometers, 0–0.75 mg/kg). The LS-SVM classification model of ALDC samples was established based on the original spectra, smoothed spectra, second-derivative (D2) spectra, and standard normal transformation (SNV) spectra, respectively. The prediction accuracy of D2-LS-SVM was the highest (0.950). FT-NIR combined with LS-SVM modeling can quickly and accurately identify the contaminated ALDC. Compared with traditional methods which rely on naked eye observation of plants, this method is objective and more sensitive and applicable.
关键词： soil,LS-SVM,FT-NIR spectroscopy,Artemisia lavandulaefolia DC.,mercury
更新于2025-09-16 10:30:52
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Soil Content Accurately Modeled Using Spectroscopy
摘要： Soil is the foundation of food production on the planet. Clay and organic carbon content of the soil are among the most influential factors in soil functions, productivity, and management. Current laboratory methods for studying clay and organic carbon are slow, highly uncertain, and expensive. Visible near-infrared spectroscopy has shown to be a powerful tool to detect and quantify molecules of interest in a sample. In an article recently published in the Soil Science Society of America Journal, researchers report on a novel method of combinatory on-the-go spectroscopy and soil electrical conductivity measurements in agricultural fields as a substitute to soil sample collection and laboratory analysis. The team used multivariate regression methods to predict soil clay and organic carbon in soil using the rapidly obtained data. They found that although the uncontrolled spectral measurement environment in the field introduced a large amount of noise in the dataset, comprehensive spectral preprocessing and redundant variable removal could still lead to accurate models. Furthermore, it was shown that spectroscopy alone could provide the best results without the need for adding electrical conductivity data. In addition to the practical applications in soil and agricultural studies, the results also have important implications for future sensor design, data processing, and soil modeling.
关键词： soil content,organic carbon,multivariate regression,spectroscopy,clay
更新于2025-09-16 10:30:52
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Near-Infrared Spectroscopic Study of Heavy-Metal-Contaminated Loess Soils in Tongguan Gold Area, Central China
摘要： Loess soil is a kind of widespread soil type in northwest China. Human engineering activities such as mining have caused numerous problems related to heavy metal pollution in soils, which threaten people’s health. The band formation mechanism of the near-infrared (NIR) spectral features in loess soils forms the theoretical basis for the study of the soil environment by hyperspectral remote sensing. Some NIR features of loess soils will shift because of the variations of the soil composition and microstructure after they adsorb heavy metal cations. In this study, we focused on the heavy metal adsorption of the illite, smectite, and illite–smectite (I/S) mixed layer in loess soils; evaluated the pollution by Nemerow indexing; applied X-ray diffraction (XRD), mid-infrared (MIR) spectral analysis, and inductively coupled plasma mass spectrometry (ICP-MS); and carefully observed the shift behavior of the MIR and NIR features. Then, the NIR bands were assigned to MIR bands according to the vibration behavior. Furthermore, the relationships between the NIR band positions and the six heavy metal cations as well as the Nemerow index were investigated via multiregression and simple linear correlation methods. Finally, the relationship obtained from the experiments was analyzed using the physical and chemical mechanisms of the heavy metal cations in the clay minerals. These findings may benefit the application of NIR and remote sensing techniques for detecting heavy-metal-polluted soils.
关键词： loess soil,combination band,Nemerow index,heavy metal contamination,near infrared
更新于2025-09-16 10:30:52
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Soil Nutrient Detection for Precision Agriculture Using Handheld Laser-Induced Breakdown Spectroscopy (LIBS) and Multivariate Regression Methods (PLSR, Lasso and GPR)
摘要： Precision agriculture (PA) strongly relies on spatially differentiated sensor information. Handheld instruments based on laser-induced breakdown spectroscopy (LIBS) are a promising sensor technique for the in-field determination of various soil parameters. In this work, the potential of handheld LIBS for the determination of the total mass fractions of the major nutrients Ca, K, Mg, N, P and the trace nutrients Mn, Fe was evaluated. Additionally, other soil parameters, such as humus content, soil pH value and plant available P content, were determined. Since the quantification of nutrients by LIBS depends strongly on the soil matrix, various multivariate regression methods were used for calibration and prediction. These include partial least squares regression (PLSR), least absolute shrinkage and selection operator regression (Lasso), and Gaussian process regression (GPR). The best prediction results were obtained for Ca, K, Mg and Fe. The coefficients of determination obtained for other nutrients were smaller. This is due to much lower concentrations in the case of Mn, while the low number of lines and very weak intensities are the reason for the deviation of N and P. Soil parameters that are not directly related to one element, such as pH, could also be predicted. Lasso and GPR yielded slightly better results than PLSR. Additionally, several methods of data pretreatment were investigated.
关键词： precision agriculture,LIBS,PLS regression,gaussian processes,soil,lasso,nutrients
更新于2025-09-16 10:30:52
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[IEEE 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Guangzhou, China (2019.5.19-2019.5.22)] 2019 International Conference on Microwave and Millimeter Wave Technology (ICMMT) - Design of Dynamically Tunable Broadband Polarization Converter in Terahertz Frequency Based on Graphene Strips
摘要： The phenomenon of soil salinization in semi-arid regions is getting amplified and accentuated by both anthropogenic practices and climate change. Land salinization mapping and monitoring using conventional strategies are insufficient and difficult. Our work aims to study the potential of synthetic aperture radar (SAR) for mapping and monitoring of the spatio-temporal dynamics of soil salinity using interferometry. Our contribution in this paper consists of a statistical relationship that we establish between field salinity measurement and InSAR coherence based on an empirical analysis. For experimental validation, two sites were selected: 1) the region of Mahdia (central Tunisia) and 2) the plain of Tadla (central Morocco). Both sites underwent three ground campaigns simultaneously with three Radarsat-2 SAR image acquisitions. The results show that it is possible to estimate the temporal change in soil electrical conductivity (EC) from SAR images through the InSAR technique. It has been shown that the radar signal is more sensitive to soil salinity in HH polarization using a small incidence angle. However, for the HV polarization, a large angle of incidence is more suitable. This is, under considering the minimal influence of roughness and moisture surfaces, for a given InSAR coherence.
关键词： interferometric synthetic aperture radar (InSAR) coherence,polarimetric synthetic aperture radar (SAR),soil salinity,Electrical conductivity (EC)
更新于2025-09-16 10:30:52
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Distributed Optical Fiber-Based Approach for Soila??Structure Interaction
摘要： Scour is a hydraulic risk threatening the stability of bridges in fluvial and coastal areas. Therefore, developing permanent and real-time monitoring techniques is crucial. Recent advances in strain measurements using fiber optic sensors allow new opportunities for scour monitoring. In this study, the innovative optical frequency domain reflectometry (OFDR) was used to evaluate the effect of scour by performing distributed strain measurements along a rod under static lateral loads. An analytical analysis based on the Winkler model of the soil was carefully established and used to evaluate the accuracy of the fiber optic sensors and helped interpret the measurements results. Dynamic tests were also performed and results from static and dynamic tests were compared using an equivalent cantilever model.
关键词： scour,fiber optic sensors,equivalent length,distributed measurements,winkler model,soil-structure interaction
更新于2025-09-16 10:30:52