Application of Laser-induced Breakdown Spectroscopy in Soil Detection
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Laser-induced breakdown spectroscopy can be used to detect the effective content of heavy met al ions in soil.The basic principle of emission spectrum from excited plasma is summarized.And the experiment apparatus are designed.A semiconductor solid state laser is used as an excitation light source and a spectrometer is used as a receiver.The spectrum lines of metal ions in selected soil are obtained.Compared with spectrum line graphs of standard metal ions,the content of heavy metal ions in soil is obtained.Whether the soil is polluted or not is determined.The experiments prove that the method is feasible to be used in soil detection.Keywords:
Laser-induced breakdown spectroscopy
Atomic emission spectroscopy
Soil test
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Laser-induced breakdown spectroscopy
Electron temperature
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Laser-induced breakdown spectroscopy
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We have successfully demonstrated the technique of laser-induced breakdown spectroscopy (LIBS) in the determination of the total concentration of carbon and nitrogen in soils. We have obtained a linear calibration curve for carbon in 15 soil samples directly correlated to the soil combustion technique.
Laser-induced breakdown spectroscopy
Carbon fibers
Soil carbon
Soil test
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Laser-induced breakdown spectroscopy
Carbon fibers
Laser Ablation
SPARK (programming language)
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Laser-induced breakdown spectroscopy(LIBS) technology for the detection of heavy metals in soils was studied against the limitation of traditional detection methods.The spectra of nine soil samples were measured and analyzed by using Nd∶YAG laser source at the pulse repetition frequency of 5 Hz and the pulse width of 8 ns and the single pulse energy of 80 mJ,and by using the AM-566 monochromator and the SR250 Boxcar.A method for calibrating the experimental device was explored.The concentration inversion curve by taking Cd element as an example is give and its relative error is about 7%.
Monochromator
Laser-induced breakdown spectroscopy
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In this work, a nickel metal mesh was used to allow a direct detection of salt in soil sample by LIBS utilizing unique characteristics of a TEA CO2. The metal mesh is placed in the front of the soil sample to prevent the soil sample from blowing off upon focusing the high pulsed laser beam irradiation. LIBS apparatus used in this work is a TEA CO2 laser operated at wavelength of 10.6 μm with pulse energy and duration of 3J and 200 ns, respectively. The laser beam was focused using a ZnSe lens (f = 200 mm) onto soil sample after passing through the metal mesh. The emission spectrum from the induced plasma was detected using an optical multichannel analyzer (OMA) system consisting of a 0.32-m-focal length spectrograph with a grating of 1200 graves/mm and a 1024-channel photodiode detector array with a micro-channel plate intensifier. The soil sample used is a standard soil and ordinary soil containing several salts such as Ca, Mg at high concentration. The LIBS experiment was carried out at high pressure surrounding gas of 1 atmosphere. It was observed that by the aid of the metal mesh, strong breakdown gas plasma can be produced just after TEA CO2 laser irradiation on soil sample without significant sample blowing off. It was found that emission lines from salts, Ca (Ca II 393. 3 nm, Ca II 396.3 nm, Ca I 422.5 nm), and also other salts including Mg and Na can clearly be detected with strong emission intensity and narrow spectral width. This result implies that a TEA CO2 LIBS assisted by the metal mesh (metal mesh method) can be used for direct analysis several salts such as Ca, Mg, and Na in soil sample.
Laser-induced breakdown spectroscopy
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The laser induced breakdown spectroscopy(LIBS) spectra of the soil are measured in the visible spectral region.The main and some trace elements of the soil sample are obtained by the analysis and assignment of spectral structure and spectral lines respectively.Additionally,the intensities of Pb 405.78 nm spectral line are measured at the different concentration of Pb in soil.The LIBS calibration curve of the analytical spectral line is obtained by internal calibration,and the value of detection limit,36.7×10-6,is obtained from the fit of the calibration curve.
Laser-induced breakdown spectroscopy
Soil test
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Laser-induced breakdown spectroscopy
Laser Ablation
Nanosecond
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Spatial confinement has great potential for Laser Induced Breakdown Spectroscopy (LIBS) instruments after it has been proven that it has the ability to enhance the LIBS signal strength and repeatability. In order to achieve in-situ measurement of heavy metals in farmland soils by LIBS, a hemispherical spatial confinement device is designed and used to collect plasma spectra, in which the optical fibers directly collect the breakdown spectroscopy of the soil samples. This device could effectively increase the stability of the spectrum intensity of soil. It also has other advantages, such as ease of installation, and its small and compact size. The relationship between the spectrum intensity and the laser pulse energy is studied for this device. It is found that the breakdown threshold is 160 cm−2, and when the laser fluence increases to 250 J/cm2, the spectrum intensity reaches its maximum. Four different kinds of laser pulse energy were set up and in each case the limits of detection of Cd, Cu, Ni, Pb and Zn were calculated. The results show that when the laser pulse fluence was 2.12 GW/cm2, we obtained the smallest limits of detection of these heavy metals, which are all under 10 mg/kg. This device can satisfy the needs of heavy metal in-situ detection, and in the next step it will be integrated into a portable LIBS instrument.
Laser-induced breakdown spectroscopy
Repeatability
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