土壤中铁元素对铬元素p-XRF测定准确度的影响与校正

便携式X射线荧光光谱仪（p-XRF）能够快速检测土壤中的铬元素，但由于土壤成分复杂、基体效应不明，导致其检测准确度较低。铁元素作为土壤基体中的主量元素，在不同类型土壤中含量变化范围大，是影响铬元素p-XRF测定准确度的主要元素之一，深入研究铁元素对铬元素荧光强度的影响有助于提高p-XRF测定土壤中铬元素的准确度。本文以人工配置的铬-铁土壤样品研究铬元素荧光强度与铬元素含量和铁元素含量的变化关系，采用经验公式校正铁元素对铬元素p-XRF分析准确度的影响。结果表明：土壤样品中的铁元素含量固定不变时，铬元素的含量与其相应的特征X射线荧光强度呈线性变化，相关系数均在0.9990以上，且铬元素荧光强度的增长速率随着土壤中铁元素含量的增加而增大；另外通过对同一铬含量、不同铁含量土壤样品的研究，验证了铁元素对铬元素的荧光增强效应，并发现该增强效应还与铁、铬元素的相互作用有关。结合铬、铁元素基体效应研究结果，本文建立了铁元素对铬元素p-XRF测定的校正方程式，相比于普通的线性回归，该方法的相关系数从0.9011提高到了0.9986，硅藻土样品的p-XRF分析平均相对误差从21.94%下降至2.52%，实际土壤样品的p-XRF分析平均相对误差从51.02%下降至5.21%。

Effect and Correction of Iron in Soil on Accuracy of Chromium Determination by Portable X-ray Fluorescence Spectrometry

BACKGROUND: The portable X-ray fluorescence spectrometer (p-XRF) can detect chromium in soil rapidly, but its detection accuracy is low because of the complexity of soil composition and the unknown matrix effect. As the main element in soil matrix, iron content varies widely in different types of soil, which is one of the main elements affecting the accuracy of p-XRF determination of chromium.
OBJECTIVES: To improve the accuracy of p-XRF in the determination of chromium in soil.
METHODS: The relationship between the fluorescence intensity of chromium and the content of chromium and iron was studied by using artificial soil samples with added chromium and iron. A calibration model was established based on research results.
RESULTS: When the content of iron in the soil sample was fixed, the content of chromium changed linearly with its corresponding characteristic X-ray fluorescence intensity, and the correlation coefficients were all above 0.9990. Moreover, the growth rate of the fluorescence intensity of chromium increased with the increase of iron content in the soil. In addition, through the study of soil samples with the same chromium content and different iron content, the fluorescence enhancement effect of iron on chromium was verified, and it was found that the enhancement effect was also related to the interaction of iron and chromium.
CONCLUSIONS: Combining the research results of matrix effects of chromium and iron, the correction equation of effect of iron on p-XRF determination of chromium has been established. Compared with ordinary linear regression, the correlation coefficient of this method increased from 0.9011 to 0.9986. The average relative error for p-XRF analysis of diatomite samples decreased from 21.94% to 2.52%, and the average relative error of p-XRF analysis of actual soil samples decreased from 51.02% to 5.21%.