基于太赫兹光谱的土壤重金属铅含量检测初步研究

Preliminary Research on Heavy Metal Pb Detection in Soil Based on Terahertz Spectroscopy

探索应用太赫兹时域光谱用于农田土壤重金属含量检测的机理和可行性,尝试发展一种新的检测方法和手段。研究了样品制备测量方法,确定了最佳的制备参数为:聚乙烯样品盒尺寸为35 mm×3.5 mm×35 mm,中间空隙1.5 mm;压片法样品质量220 mg,2.5 t压力;分别制作一定浓度梯度(30~900 mg/kg)的含铅土壤样品30组,使用Z-2型太赫兹时域光谱仪采集相应的土壤样品太赫兹透射光谱数据,对光谱数据进行预处理,包括平滑处理、多元散射校正、基线校正,采用全谱-偏最小二乘法、区间-偏最小二乘法和遗传算法-偏最小二乘法建立土壤样品中重金属元素铅含量的定标模型并对预测集样本进行预测。实验结果表明,采用样品盒法制作土壤样品并且基于遗传算法进行特征波段选择、结合偏最小二乘法的建模效果最佳,含重金属铅的土壤样本模型的标定集和预测集的相关系数分别为0.86和0.81,标定均方根误差和预测均方根误差分别为23.55 mg/kg和39.52 mg/kg。本研究通过分析土壤样品的太赫兹透射光谱吸收系数与重金属元素铅含量的相关关系,建立了较好的预测模型。

In order to realize the detection of heavy metal Pb2 +in soil,the content of heavy metal Pb element in soil was detected by terahertz spectroscopy. The relationship between spectral absorption rate and Pb2 +content in soil was analyzed. A basic method for the detection of heavy metal content in soil by terahertz technology was provided. The soil samples with a certain concentration gradient( 30 ~ 900 mg / kg)were produced by sample holder method and pressed-slice method. The spectral data of terahertz transmission soil were collected and pre-processed,including smoothing,multiple scatter correction and baseline correction. The model of heavy metal Pb2 +element in soil samples was established by using the method of full spectral,interval partial least squares and genetic algorithm,respectively. The results showed that the model established by sample box method and genetic algorithm method was the optimal one. The correlation coefficients of calibration set and prediction set were 0. 86 and 0. 81,root mean square errors of calibration set and prediction set were 23. 55 mg / kg and 39. 52 mg / kg,respectively.This research provided a theoretical and methodological reference for important parameters detection offarmland soil using terahertz and the preliminary applications research of terahertz.