为了提高土壤重金属激光诱导击穿光谱(LIBS)光谱稳定性和定量反演准确性, 设计了半球形空间约束结构,研究了重金属LIBS光谱相对标准偏差(RSD)和预测相对误差(REP)。采用多次平均和内标法对光谱数据进行处理, 增加脉冲次数和内标法使光谱RSD分别降低1.59%和3.65%,提高了光谱稳定性。对比分析了单变量和最小偏二乘法(PLS)方法下样品 浓度的REP,四条特征谱线CrI:357.869 nm、CrI:359.349 nm、CrI:425.435 nm和CrI:427.480 nm单变量方法对样品 的REP 分别为9.42%、8.43%、6.16%和7.79%, 4种变量组合下PLS对样品的REP分别为3.70%、4.10%、4.83%和4.67%。PLS方法 最大使得样品REP减小5.72%,提高了定量反演的准确性。以上研究结果为提高土壤重金属LIBS分析能力提供了数据和方法支持。

In order to improve spectral stability and quantitative inversion accuracy of heavy metal in soil by laser induced breakdown spectroscopy (LIBS), hemispherical space constraint structure has been designed, the relative standard deviation (RSD) and relative error of prediction (REP) of LIBS of heavy metals are studied. Multiple average and internal standard method are used to process spectral data, the RSD of spectrum has been reduced 1.59% and 3.65% respectively by increasing the number of pulses and internal standard method, and the spectral stability has been improved. The REP of sample concentration is comparatively analyzed under univariate and patial least squares (PLS) method, REP of univariate method of four characteristic spectral lines CrI: 357.869 nm, CrI: 359.349 nm, CrI: 425.435 nm and CrI: 427.480 nm are 9.42%、8.43%、 6.16% and 7.79% respectively, the REP of PLS under four variable combination are 3.70%、4.10% 、4.83% and 4.67% respectively. The REP of sample is reduced 5.72% by PLS method, and the accuracy of quantitative inversion is improved. The above results provide data and method support for improving analytical ability of LIBS of heavy metals in soil.