基于NELIBS技术和EN-SVR模型的生物炭中水溶态P元素定量检测研究

Quantitative Determination of Water-Soluble P in Biochar Based on NELIBS Technology and EN-SVR Model

生物炭还田能够提供大量植物可吸收利用的有效态磷。采用激光诱导击穿光谱(LIBS)技术对秸秆基生物炭中水溶态磷(P)元素进行定量检测研究。首先选用疏水性的聚乙烯平板作为液固转换基底以降低液滴干燥后基底表面严重的“咖啡环效应”。为解决生物炭中水溶态P元素LIBS信号低灵敏度问题,研究并探讨了3种粒径金纳米颗粒(Au nanoparticles,AuNPs)对P元素4条分析谱线的信号增强性能。结果表明大粒径(73 nm和105 nm)的金纳米颗粒更容易发生聚集效应,并且光谱信噪比较大。进一步地比较分析了3种粒径金纳米颗粒增强后P元素的单变量校正曲线模型效果,45 nm的金纳米颗粒信号增强后的单变量校正曲线模型效果均最优。将该粒径金纳米颗粒增强后的4条分析谱线展宽波段光谱用于弹性网络-支持向量回归(EN-SVR)模型构建,其最优模型的预测平均误差(ARP)和预测相对标准偏差(RSDP)分别为5.40%和11.09%。研究结果表明纳米颗粒增强激光诱导击穿光谱(NELIBS)结合EN-SVR模型可以用于生物炭中水溶态P元素精确定量检测。

Biochar can provide many available phosphorus(P)that can be absorbed and utilized by plants.In this paper,laser-induced breakdown spectroscopy(LIBS)was used to detect water-soluble P in straw based biochar quantitatively.To reduce the serious“coffee ring effect”on the substrate’s surface after droplet drying,hydrophobic polyethylene plate was selected as the liquid-solid conversion substrate.To solve the problem of the low sensitivity of LIBS signal of water-soluble P element in biochar,the signal enhancement performance of three kinds of Au nanoparticles(AuNPs)on four analytical lines of P element was studied and discussed.The results show that Au nanoparticles with large particle size(73 and 105 nm)are more prone to the aggregation effect,and the spectral signal-to-noise ratio is large.Furthermore,the P element’s univariate calibration curve models enhanced by three kinds of particle size Au nanoparticles were compared and analyzed.The results show that the univariate calibration curve models with 45 nm Au nanoparticles signal enhancement are the best.Finally,the four enhanced spectral broadening bands enhanced by the Au nanoparticles were used to develop the ElasticNet-support vector regression(EN-SVR)model.The average error of the prediction set(ARP)and the relative standard deviation of the prediction set(RSDP)of the optimal model were 5.40%and 11.09%,respectively.The results show that nanoparticle enhanced laser induced breakdown spectroscopy(NELIBS)combined with the EN-SVR model can be used for the accurate quantitative determination of water-soluble P in biochar.