高精度便携式X射线荧光光谱仪在污染农田土壤重金属速测中的应用研究

Use of high-precision portable X-ray fluorescence spectrometer on the heavy metal rapid determination for contaminated agricultural soils

针对便携式X射线荧光光谱(PXRF)法中的高精度便携式X射线荧光光谱(HDXRF)法进行检出限(Cd元素)、稳定性和土壤标准物质准确性的测试,同时对农田土壤中主要重金属元素Cu、Zn、Pb、Cd和类金属As进行快速测定,并将测定结果分别与原子吸收光谱(AAS)法、原子荧光光谱(AFS)法及电感耦合等离子体发射光谱(ICP-AES)法的测定结果建立线性回归方程,以期分析土壤粒径、水分、有机质及土壤类型对测定结果的影响。结果表明:HDXRF法测定土壤中重金属的稳定性高、准确度高、检测限低,对Cd元素的检测下限为0.27 mg·kg-1。颗粒粒径对土壤重金属浓度测定结果有一定影响,样品过100目筛时的测定结果较理想;土壤含水量对HDXRF法的测定结果影响较大,应保证测试土壤样品干燥;有机质对HDXRF法的测定结果存在影响,但可通过调整方程的常数进行校准。HDXRF法测定值更接近实验室ICP-AES法的测定结果,Cu、Zn、Pb和Cd的决定系数分别为0.997 5、0.996 7、0.961 4和0.995 4;HDXRF法与实验室AFS法测定As的决定系数最高可达0.979 8。相比于实验室测定方法,HDXRF法只需简单的前处理,如风干、研磨等,且HDXRF法测定范围宽,适用于土壤中重金属Cu、Zn、Pb、Cd和类金属As的快速测定,是一种简单、快速、准确、可靠的分析方法。

In this paper,the detection limit(cadmium),stability and the accuracy of reference material of soil were tested by high precision portable X-ray fluorescence(HDXRF)spectrometer in PXRF and HDXRF spectrometer was used to detect the main heavy metal or metalloid elements include copper,zinc,lead,cadmium and arsenic in agricultural soils and linear regressions were established for the determina?tion results of HDXRF spectrometry with atomic absorption spectrometry(AAS),atomic fluorescence spectrometry(AFS)and inductively coupled plasma atomic emission spectrometry(ICP-AES)respectively.Furthermore,the effects of soil particle size,moisture content,organic matter content and soil type on the determination results were also investigated.The results show that:HDXRF spectrometry has high stability,high accuracy and low detection limit for heavy metals and the lower detection limit for cadmium(Cd)is 0.27 mg·kg^-1.The particle size of soil samples affected HDXRF performance and 150μm is a better choice.The moisture content of the soil samples had a significant influence on the results of HDXRF spectrometry,so samples should be kept dry.The soil organic matter content has an influence on the determination of HDXRF spectrometry,but it can be calibrated by adjusting the constant of equation.The determination results of HDXRF spectrometry are more close to the results by ICP-AES method and the determination coefficients of copper(Cu),zinc(Zn),lead(Pb)and Cd are 0.997 5,0.996 7,0.961 4 and 0.995 4,respectively.The determination coefficients of As determined by HDXRF spectrometry and traditional laboratory AFS is 0.979 8.Compared with the traditional laboratory measurement methods,the soil samples can be analyzed HDXRF spectrometry just only after simple pretreatment,such as air dried and grinded.Therefore,HDXRF spectrometry is a simple,fast,accurate and reliable analysis method which can be widely used in the determination of heavy metal Cu,Zn,Pb,Cd and As in soil.