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采用激光诱导击穿光谱(LIBS)对土壤中的营养元素进行了定量检测。采用输出波长为1064nm、脉宽为5.82ns的Nd…YAG脉冲激光器作为光源,将激光聚焦在土壤表面产生激光诱导等离子体,使用三光栅光谱仪和门宽控制的增强电荷耦合器件(ICCD)测量等离子体发射光谱。基于传统LIBS系统,新增了扩束镜系统和实时监测系统,研制了笼式结构LIBS系统,优化了笼式结构中扩束镜系统的激光聚焦位置,获得了最佳的激光聚焦位置0.2cm。测试了MgⅡ279.56nm、MgⅡ 280.26nm和MgⅠ 285.21nm谱线的信号强度。结果表明,笼式结构LIBS系统在信号稳定性上优于传统LIBS系统。定量分析了土壤中营养元素Cu、Mn、Mg、K的质量分数,它们的检出限分别为0.42×10~(-6)、13.2×10~(-6)、38.5×10~(-6)、62×10~(-6),优于传统LIBS系统得到的检出限。基于定标模型预测了土壤中Cu、Mn、Mg、K元素的质量分数,它们预测值的平均相对误差分别为9.2%、9.6%、8.5%、10.9%。
The nutrient elements in soil were quantitatively detected by laser induced breakdown spectroscopy (LIBS). A Nd: YAG pulsed laser with an output wavelength of 1064 nm and a pulse width of 5.82 ns was used as a light source to focus the laser on the surface of the soil to generate a laser-induced plasma. The plasma was measured using a triple-grating spectrometer and a gate charge control device (ICCD) Body emission spectra. Based on the traditional LIBS system, a new beam expander system and real-time monitoring system are added. A cage-structured LIBS system is developed to optimize the laser focusing position of the beam expander system in the cage structure. The optimal laser focusing position is 0.2 cm . The signal intensities of Mg II 279.56 nm, Mg II 280.26 nm and Mg I 285.21 nm lines were tested. The results show that the cage structure LIBS system is superior to the traditional LIBS system in signal stability. The mass fractions of Cu, Mn, Mg and K in soil were quantitatively analyzed. The detection limits were 0.42 × 10 -6, 13.2 × 10 -6, 38.5 × 10 -6 ), 62 × 10 ~ (-6), which is better than that of the traditional LIBS system. Based on the calibration model, the mass fractions of Cu, Mn, Mg and K in soils were predicted. The average relative errors of their predicted values were 9.2%, 9.6%, 8.5% and 10.9% respectively.