| With the development of modern society, the heavy metal pollution in soil is becomingmore and more serious, which has directly influence on the ecological environment andhuman health. Therefore, rapidly quantitative detecting the heavy metal pollutants in soil isof great significance. Common heavy metal detection methods have flame atomicabsorption spectrometry (FLAA), graphite furnace atomic absorption spectrometry(GFAA), inductively coupled plasma mass spectrometry (ICP-MS) and so on. Though thedetection sensitivity is higher, those methods have a number of weaknesses, such ascomplicated analysis, longer analyzing cycle, poor real-time measurement andmonoelement analyzing and so on. Selecting Poyang Lake bottom soil as the researchobject, this paper raised a method-laser induced breakdown spectroscopy (LIBS), whichrapid and quantitative analysis of heavy metal in soil. LIBS is a qualitative and quantitativeanalytical technology based on atomic emission spectrum which has many advantages,such as shorter analyzing cycle, simpler structure, less damage to the analysis objects,remote analysis and multi-element analyzing simultaneously etc.It’s adaptive to variousbad environments and real-time online detection. So, it is significant in real-timemonitoring the environmental quality as well as in other fields. This technology has greatpotential applications. This paper includes the following content:Firstly, the LIBS experiment system was set up. The system mainly was composed byNd: YAG laser, spectrometer, rotating platform, DG535, computer and Optical devices. Alaser was emitted when DG535triggered the Nd: YAG laser, the laser beam after reflectorand lens focused on the sample surface. The plasmas that on the surface of sample werecollected through spectrometer and the spectral data be analyzed by computer.Secondly, the soil samples were prepared by a simple and rapid method. According todifferent research purposes, soil samples were divided into the natural soil and the nationalstandard material soil. Natural soils were taken from RaoHe which is the most seriouslyheavy metals contaminated areas of Poyang Lake valley. National standard substances ofsoil were purchased from National Institute of Metrology P.R.China. In order to improvethe stability of the LIBS, Natural soils need simple and quick pre-process such as drying,crushing, grinding, and screening. Then natural soil sample and the standard soil sampleswere fast manual preparation of pressed.Then, several working conditional parameters for influencing LIBS detection indetecting heavy pollution in soil such as laser energy, latency time, and pulse cumulativefrequency have been optimized. The results showed optimal parameters is110mJ,840nsand40times respectively. Besides some characteristic spectral line selection principle areprovided. The spectral lines Cr I425.43nm, PbI405.78nm, BaII455.41nm and SrI460.73nm are selected as analytical lines.Finally, the intensity-concentration calibration method, the internal standard method, theintensity ratio calibration method and partial least square method for the quantitativeanalysis were used to analyze Pb, Cr, Ba, Sr in soil samples, and calibration curves ofanalyzing elements were established. By comparing the prediction results of these modelswith the actual results, verify the feasibility of LIBS for rapid measurement of heavy metalelements in soil. |
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