波长色散X射线荧光光谱法测定土壤和水系沉积物中13种重金属元素

重金属是土壤和水系沉积物环境监测的重要指标,由于土壤和水系沉积物样品基体复杂,采用X射线荧光光谱法(XRF)测定其中重金属元素,合理地优化测定条件对提高分析方法的准确度非常关键。以粉末压片法制样,建立了XRF测定土壤和水系沉积物等环境样品中As、Cd、Co、Cr、Cu、Mn、Mo、Ni、Pb、Sb、Sn、V、Zn等13种重金属元素的分析方法。选用31件一级土壤、水系沉积物和岩石成分分析标准物质拟合校准曲线,探讨了各元素的测定条件,以及谱线重叠干扰和基体效应校正等问题,提出了提高As、Cd、Co、Mo、Ni、Sb、Sn等痕量重金属元素分析准确度的具体措施。选用重金属含量水平不同的2件土壤样品考察分析方法的精密度,对含量10mg/kg以上的元素,其测定结果的相对标准偏差(RSD)分别为0.47%~5.3%(日内,n=12)和0.83%~6.3%(日间,n=12)。方法的检出限在0.39~5.1mg/kg之间。选用4件土壤和水系沉积物标准物质评估方法的正确度,重金属元素的测量结果与认定值一致。建立的分析方法检出限、精密度和正确度满足土壤和水系沉积物环境监测分析的技术要求。与标准方法相比,建立的分析方法增加了Cd、Sb、Sn等3个重金属元素,拓宽了痕量元素的分析范围。

Determination of thirteen heavy metals in soil and stream sediment by wavelength dispersive X-ray fluorescence spectrometry

Heavy metals are important indexes for the environmental monitoring of soil and stream sediment. Since the matrix of soil and stream sediment samples is complex, the reasonable optimization of determination conditions is very import to improve the accuracy of analysis method when the contents of heavy metals are determined by X-ray fluorescence spectrometry (XRF). The analysis method of 13 heavy metal elements (including As, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Sn, V and Zn) in environmental samples such as soil and stream sediment by XRF was established after sample preparation by powder pressed pellet. Total 31 certified reference materials of primary soil, stream sediment and rock were employed to fit the calibration curve. The determination conditions of elements were discussed. The spectral overlapping interference and matrix effect correction were also investigated. The detailed measures to improve the analysis accuracy of trace heavy metals (including As, Cd, Co, Mo, Ni, Sb and Sn) were proposed. The precision of analysis method was investigated using two soil samples with different contents of heavy metals. For the elements with content higher than 10mg/kg, the relative standard deviations (RSD, n=12, within one day) of measurements results were 0.47%-5.3% (within one day) and 0.83%-6.3% (in days), respectively. The detection limits ranged from 0.39mg/kg to 5.1mg/kg. Four certified reference materials of soil and stream sediment were used to evaluate the trueness of method. The found results of heavy metals were consistent with the certified values. The proposed method could meet the technical requirements of environmental monitoring of soil and stream sediment in detection limit, precision and trueness. Compared with the standard methods, the analysis of three heavy metals (Cd, Sb and Sn) was added in the proposed method, which broadened the analysis range of trace elements.