基于不同化学计量学方法的土壤重金属激光诱导击穿光谱定量分析研究

工业的发展及城市化进程的深入，造成大量耕地土壤遭受重金属污染，土壤重金属元素的准确检测对制定土壤重金属防治决策提供有效参考。本研究应用激光诱导击穿光谱(LIBS)结合化学计量学方法对土壤中的铅(Pb)和镉(Cd)元素进行定量分析。根据土壤重金属污染的不同程度，人为制作了含有Pb和Cd元素的15个浓度梯度的土壤样本，并采集各个样本的LIBS谱线。采用剔除异常光谱和数据归一化来减少试验误差和噪声。综合土壤LIBS发射谱线中Pb和Cd元素谱峰信息以及美国国家标准与技术研究院(NIST)的标准原子光谱数据库，选取了Pb，Cd元素的分析谱线与分析谱线区间，对比分析基于多元线性回归(MLR)、偏最小二乘回归(PLSR)、最小二乘支持向量机(LS-SVM)和反向传播人工神经网络(BP-ANN)算法，建立分析谱线区间与对应Pb和Cd元素浓度之间的定量回归模型。结果表明，非线性的LS-SVM和BP-ANN的模型的预测性能优于线性MLR和PLSR模型，这可能是因为非线性模型能够通过自适应较好地解决土壤基体效应的影响。研究表明，LIBS技术结合多元化学计量学方法能够为土壤重金属准确检测提供新的分析手段，为制定农业土壤重金属防治决策提供有效的理论基础。

Comparative Analysis of Chemometrics Method on Heavy Metal Detection in Soil with Laser-Induced Breakdown Spectroscopy

A large number of farm lands are contaminated by heavy metals in the process of industrialization and urbanization . Precise detection of heavy metals in soil offers valid reference for prevention and recovery of heavy metals in the field .In this re-search ,Laser induced breakdown spectroscopy (LIBS) and chemometrics methods were employed to conduct quantitative analy-sis of heavy metals Pb and Cd in soil .Based on the pollution extent ,soil samples with 15 concentration gradients of Pb and Cd were manually made up .Then ,the LIBS emission lines of all soil samples were collected firstly .In order to eliminate errors and noise of spectral data ,preprocessing methods called removal of abnormal data and normalization were used .Then ,characteristic lines and spectral regions of Pb and Cd were determined based on our LIBS spectra and Atomic Spectra Database (ASD) of Na-tional Institute of Standards and Technology (NIST) .Quantity regression models based on multiple linear regression (MLR) , partial least squares regression (PLSR) ,least squares support vector machine (LS-SVM ) and back propagation-artificial neural network (BP-ANN) were set up and their results were compared .As a result ,models based on non-linear methods (LS-SVM and BP-ANN) offered a promising results than the linear methods of MLR and PLSR .The probable reason was that non-linear methods had an advantage to deal with matrix effects of soil automatically .The results indicated that LIBS coupled with multiple chemometrics methods provided a brand-new analysis approach for heavy metals accurate detection in soil and it could be consid-ered as an effective theoretical foundation of making protection and recovery decision for soil contaminated by heavy metals .