Characterization Of Laser Induced Soil Plasma

In recent years,the national economy has grown at a rapid rate,and the quality of life of the people has improved.At the same time,environmental problems have become more severe,with soil pollution being particularly prominent.Research on the characterization of soil plasma can obtain information on soil pollution.Laser-induced breakdown spectroscopy is very suitable for the analysis and detection of soil elements because of its fast analysis speed,simple sample pretreatment and multi-element synchronous detection.In this paper,the current research status of laser induced breakdown spectroscopy in soil element detection is analyzed,and the theory of laser plasma is introduced.The experimental system is built according to the principle of LIBS.Combined with theoretical analysis and experimental research,the following research work has been carried out on the characterization of laser plasma and the application of LIBS in soil testing:Optimization of experimental parameters for the LIBS system.In order to improve the accuracy and stability of the results of laser induced breakdown spectroscopy,this paper studies the influence of the main parameters of the experimental system(whether the ablation position is the same,laser energy,lens focal length,relative position of lens and sample)on the soil plasma characteristics,and finally determines the optimal detection conditions in the laboratory environment: laser energy It is 21 mJ,the focal length of the lens is 15 cm,the sample is constantly moving and the surface is located 2mm in front of the laser focus,which provides a reference for the qualitative and quantitative analysis of the soil.Qualitative analysis of soil elements.After collecting the spectrum of the soilplasma,the elements are assigned according to the selection principle of the analytical line and the basic method of element attribution.The analysis results show that the soil samples contain not only basic elements such as N,P,K,Al,Ca,Si,Fe,but also trace elements such as Cu,Pb,Zn,Ni,Co,Hg and Cr.At the same time,the electron temperature of the soil plasma was calculated to be 13341 K,and the electron density was 1.424×1017cm-3.Quantitative analysis of soil elements.In this paper,the free calibration method was chosen as the quantitative analysis method for soil testing,and the reliability of the free calibration method was verified by 304 stainless steel.Then,in order to improve the accuracy of the results of calibration free-laser induced breakdown spectrum(CF-LIBS),the self-absorption effect was corrected by the internal standard line self-absorption correction method.Finally,the content of elements in the soil samples was calculated and the soil pollution status was analyzed.