便携式X射线荧光仪测定土壤中镍的精度研究

作为一种快速、现场检测的分析方法，便携式X射线荧光光谱(FP-XRF)可以在土壤重金属分析领域获得广泛应用。然而，FP-XRF的测定精度受到一些因素的影响，制约了它的应用。前人的研究已经发现，当元素含量较低时，FP-XRF的测定精度不佳。在现场检测时也会受到土壤湿度效应和粒径的影响。但是尚未有研究对上述因素的影响类型和影响程度进行深入探究。本文以Ni为例，根据准确度和精密度，研究了Ni含量与FP-XRF测定精度的关系，得出了这种影响的临界值;比较了现场测定中土壤湿度效应和粒径对准确度和精密度的影响程度。实验表明,FP-XRF的测定精度与Ni含量相关，临界值为400 mg·kg-1。Ni的浓度低于400 mg·kg-1时，相对标准偏差(RSD)和相对不确定度同时降低，即测定精度随着Ni含量的升高而提高;Ni的浓度高于于400 mg·kg-1时相对标准偏差(RSD)和相对不确定度不再有明显变化，即测定精度不再与Ni含量有关。现场检测中，土壤水分贡献的相对不确定度为3.77%，粒径贡献的相对不确定度为0.56%。土壤湿度效应对准确度和精密度的影响程度都要高于土壤粒径。

Evaluation of Field Portable X-Ray Fluorescence Performance for the Analysis of Ni in Soil

As a rapid, in-situ analysis method, Field portable X-ray fluorescence spectrometry (FP-XRF) can be widely applied in soil heavy metals analysis field. Whereas, some factors may affect FP-XRF performance and restrict the application. Studies have proved that FP-XRF has poorer performance when the concentration of target element is low, and soil moisture and particle size will affect FP-XRF performance. But few studies have been conducted in depth. This study took an example of Ni, demonstrated the relationship between Ni concentration and FP-XRF performance on accuracy and precision, and gave a critical value. Effects of soilmoisture and particle size on accuracy and precision also had been compared. Results show that, FP-XRF performance is related to Ni concentration and the critical value is 400 mg·kg-1. Relative standard deviation (RSD) and relativeuncertainty decrease while the Ni concentration is below 400 mg·kg-1, hence FP-XRF performance improves with increasing Ni concentration in this range;RSD and relative uncertainty change little while the Ni concentration is above 400 mg·kg-1, hence FP-XRF performance does not have correlation with Ni concentration any more. For in-situ analysis, the relative uncertainty contributed by soil moisture is 3.77%, and the relative certainty contributed by particle size is 0.56%. Effect of soil moisture is evidently more serious than particle size both on accuracy and precision.