School of Environmental and Rural Science, University of New England, Armidale 2351, Australia.
School of Environmental and Rural Science, University of New England, Armidale 2351, Australia.
Environ Int. 2020 Jan;134:105250. doi: 10.1016/j.envint.2019.105250. Epub 2019 Nov 18.
Portable XRF is a rapid, mobile, high throughput, and potentially cost effective instrumental analytical technique capable of elemental assessment. It is widely used for environmental assessment of soils in a variety of contexts such as agriculture and pollution both in-situ and ex-situ, to varying levels of success. Portable XRF performance for soil analysis is often validated against wet chemistry techniques but a range of factors may give rise to elementally dependent disparities affecting accuracy and precision assessments. These include heterogeneity, analysis times, instrument stability during analyses, protective thin films, incident X-rays, sample thickness, sample width, analyte interferences, detector resolution, power source fluctuations and instrumental drift. Light elements comprising water and organic matter (i.e. carbon, oxygen) also negatively affect measurements due to X-ray scattering and attenuation. The often-overlooked phenomenon of variability in both soil organic matter and water can also affect soil density (e.g. shrink-swell clays) and thus sample critical thickness which in turn affects the effective volume of sample analyzed. Compounding this, for elements having lower characteristic fluorescence energy, effective volumes of analyses are lower and thus measurements may not be representative of the whole sample. Understanding the effects and interplay between determined elemental concentrations and soil organic matter, water, and critical thickness together with the subtlety of theoretical effective volumes of analyses will help analysts mitigate potential problems and assess the applicability, advantages and limitations of PXRF for a given site. We demonstrate that with careful consideration of these factors and a systematic approach to analysis which we summarize and present, PXRF can provide highly accurate results.
便携式 X 射线荧光（Portable XRF）是一种快速、移动、高通量且具有潜在成本效益的仪器分析技术，能够进行元素评估。它广泛用于各种环境背景下（如农业和污染）的土壤环境评估，原位和异位，取得了不同程度的成功。便携式 X 射线荧光（Portable XRF）在土壤分析中的性能通常通过湿化学技术进行验证，但一系列因素可能会导致元素依赖性差异，从而影响准确性和精密度评估。这些因素包括不均匀性、分析时间、分析过程中仪器稳定性、保护薄膜、入射 X 射线、样品厚度、样品宽度、分析物干扰、探测器分辨率、电源波动和仪器漂移。包含水和有机物（即碳、氧）的轻元素也会由于 X 射线散射和衰减而对测量产生负面影响。土壤有机质和水分的变异性往往被忽视，也会影响土壤密度（例如收缩-膨胀粘土），从而影响样品临界厚度，进而影响分析的有效样品体积。更糟糕的是，对于特征荧光能量较低的元素，分析的有效体积较低，因此测量结果可能不能代表整个样品。了解确定的元素浓度与土壤有机质、水和临界厚度之间的相互作用和影响，以及理论分析有效体积的细微差别，将有助于分析人员减轻潜在问题，并评估 PXRF 在特定地点的适用性、优势和局限性。我们证明，通过仔细考虑这些因素以及我们总结和呈现的系统分析方法，PXRF 可以提供高度准确的结果。
