余克强, 赵艳茹, 刘飞, 何勇. 激光诱导击穿光谱技术检测土壤中的铅和镉含量[J]. 农业工程学报, 2016, 32(15): 197-203. DOI: 10.11975/j.issn.1002-6819.2016.15.027
    引用本文: 余克强, 赵艳茹, 刘飞, 何勇. 激光诱导击穿光谱技术检测土壤中的铅和镉含量[J]. 农业工程学报, 2016, 32(15): 197-203. DOI: 10.11975/j.issn.1002-6819.2016.15.027
    Yu Keqiang, Zhao Yanru, Liu Fei, He Yong. Laser-induced breakdown spectroscopy for determining content of Pb and Cd in soil[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(15): 197-203. DOI: 10.11975/j.issn.1002-6819.2016.15.027
    Citation: Yu Keqiang, Zhao Yanru, Liu Fei, He Yong. Laser-induced breakdown spectroscopy for determining content of Pb and Cd in soil[J]. Transactions of the Chinese Society of Agricultural Engineering (Transactions of the CSAE), 2016, 32(15): 197-203. DOI: 10.11975/j.issn.1002-6819.2016.15.027

    激光诱导击穿光谱技术检测土壤中的铅和镉含量

    Laser-induced breakdown spectroscopy for determining content of Pb and Cd in soil

    • 摘要: 为了满足土壤重金属快速准确检测的需求,同时为土壤的重金属污染防治和农业的可持续发展提供理论指导,该研究利用激光诱导击穿光谱(laser-induced breakdown spectroscopy,LIBS)技术结合定标曲线法和化学计量学方法对土壤中重金属铅(Pb)和镉(Cd)元素进行定量分析。在获取LIBS数据之后,结合土壤LIBS发射谱线中Pb和Cd谱峰信息以及美国国家标准与技术研究院(national institute of standards and technology,NIST)的标准原子光谱数据库,选取了Pb和Cd的特征谱线分别为Pb I 405.78和Cd I 361.05 nm。首先对谱线信息进行预处理后,根据谱峰信息和元素的含量,分别建立了基于谱线峰强度、归一化后洛伦兹拟合强度、谱峰积分强度与对应元素浓度之间的关系模型和定标曲线。对于Pb元素的3种定标方法得到的线性关系的决定系数(R2)分别为0.983 85、0.970 97、0.993 21,且模型反演的结果与实际值的相对误差较小;而Cd元素的3种定标方法没有得到明显线性关系。然后运用偏最小二乘回归(partial least-squares regression,PLSR)建立了土壤Pb和Cd元素的定量分析模型,Pb元素PLSR模型的结果与定标曲线法的结果类似,其预测的相关系数(RP)为0.948 5,预测均方根误差(RMSEP)为2.044 mg/g;而Cd元素的PLSR模型的结果比起定标曲线法有较大提升,其预测的相关系数(RP)为0.994 9,预测均方根误差(RMSEP)为97.05 μg/g,结果说明PLSR方法在光谱化学分析领域中比定标曲线法进行定量分析有更好的适用性。研究表明,LIBS技术能够实现对土壤重金属Pb和Cd含量的定量检测,为开发实时便携式LIBS土壤重金属检测仪提供了理论基础。

       

      Abstract: At present, a large tract of farmland or soil may be contaminated by heavy metal, which could make agricultural products polluted, bringing a harmful effect on human health.Hence, it is necessary to determine the heavy metal concentration in farmland soil.Rapid detection of heavy metals in soil is a key point of information acquirement tools in precision agriculture, and it also provides a base on prevention soil heavy metal pollution and sustainable development of agriculture.The traditional techniques for determining heavy metals is high in cost, time-consuming, use of large amount of chemicals, complex in sample preparation, and expensive in experimental device, etc.Laser-induced breakdown spectroscopy (LIBS), a form of atomic emission spectroscopy (AES), is regarded as a useful tool for rapid, real-time and in situ measurements because of its unique characteristics, such as no or less sample preparation, multi-element analysis, direct measurement without contact with the materials, stand-off or remote analysis and high detecting speed.Relying on those unique capabilities, LIBS technique has a tremendous growth and been widely applied in variety of areas, such as environmental monitoring, geological applications, biomedical detection, industrial analysis, agriculture and food.In order to evaluate the feasibility of determining the heavy metals in soil, in this research, we employed LIBS technology combined with calibration curve and chemometrics methods to quantitatively analyze the content of Pb and Cd in soil samples.Soil samples with different Pb and Cd concentration were prepared.A laboratorial LIBS device working in air was employed to obtain the spectra of soil samples.Based on analysis of LIBS curves and the data from atomic spectra database in national institute of standards and technology (NIST), emission lines at Pb I 405.78 and Cd I 361.05 nm (I was atomic spectral line) were identified as characteristic lines.Then, models and calibration curves based on LIBS intensity, Lorentz fit intensity after normalized, peak areas and corresponding content were established and fitted.For Pb element, the linear relationships of coefficient of determination (R2) of three methods were: 0.98385, 0.97097 and 0.99321, respectively.And Cd element failed to provide an effective linear relationship.Meanwhile, PLSR (Partial Linear Square Regression) model for predicting Pb and Cd were built and results demonstrated that the calibration curve and PLSR model provided similar performance, resulting in correlation coefficient of 0.9485 and root mean square error of 2.044 mg/g in the prediction set.And PLSR model for Cd element prediction revealed the promising results, resulting in correlation coefficient of 0.9949 and root mean square error of 97.05 μg/g in the prediction set.The achievements of the research not only provides a guide for detecting heavy metals in soil, but also lays a theoretical foundation for development of the portable LIBS detector used in the field.

       

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