Department of Plant and Soil Science, University of Pretoria, Pretoria, South Africa.
Department of Plant and Soil Science, Texas Tech University, Lubbock, TX, USA.
J Environ Manage. 2018 Mar 15;210:210-225. doi: 10.1016/j.jenvman.2018.01.003.
Elemental concentrations in vegetation are of critical importance, whether establishing plant essential element concentrations (toxicity vs. deficiency) or investigating deleterious elements (e.g., heavy metals) differentially extracted from the soil by plants. Traditionally, elemental analysis of vegetation has been facilitated by acid digestion followed by quantification via inductively coupled plasma (ICP) or atomic absorption (AA) spectroscopy. Previous studies have utilized portable X-ray fluorescence (PXRF) spectroscopy to quantify elements in soils, but few have evaluated the vegetation. In this study, a PXRF spectrometer was employed to scan 228 organic material samples (thatch, deciduous leaves, grasses, tree bark, and herbaceous plants) from smelter-impacted areas of Romania, as well as National Institute of Standards and Technology (NIST) certified reference materials, to demonstrate the application of PXRF for elemental determination in vegetation. Samples were scanned in three conditions: as received from the field (moist), oven dry (70 °C), and dried and powdered to pass a 2 mm sieve. Performance metrics of PXRF models relative to ICP atomic emission spectroscopy were developed to asses optimal scanning conditions. Thatch and bark samples showed the highest mean PXRF and ICP concentrations (e.g., Zn, Pb, Cd, Fe), with the exceptions of K and Cl. Validation statistics indicate that the stable validation predictive capacity of PXRF increased in the following order: oven dry intact < field moist < oven dried and powdered. Even under field moist conditions, PXRF could reasonably be used for the determination of Zn (coefficient of determination, R 0.86; residual prediction deviation, RPD 2.72) and Cu (R 0.77; RPD 2.12), while dried and powdered samples allowed for stable validation prediction of Pb (R 0.90; RPD 3.29), Fe (R 0.80; RPD 2.29), Cd (R 0.75; RPD 2.07) and Cu (R 0.98; RPD of 8.53). Summarily, PXRF was shown to be a useful approach for quickly assessing the elemental concentration in vegetation. Future PXRF/vegetation research should explore additional elements and investigate its usefulness in evaluating phytoremediation effectiveness.
植物中的元素浓度非常重要，无论是确定植物必需元素的浓度（毒性与缺乏）还是研究植物从土壤中不同程度提取的有害元素（例如重金属）。传统上，通过酸消解促进对植物中元素的分析，然后通过电感耦合等离子体（ICP）或原子吸收（AA）光谱法进行定量。先前的研究已经利用便携式 X 射线荧光（PXRF）光谱法来量化土壤中的元素，但很少有研究评估植被中的元素。在这项研究中，我们使用 PXRF 光谱仪扫描了罗马尼亚受冶炼厂影响地区的 228 种有机材料样本（草皮、落叶、草、树皮和草本植物）以及美国国家标准与技术研究院（NIST）认证的参考材料，以展示 PXRF 在植被中元素测定的应用。样品在三种条件下进行扫描：从现场接收（湿润）、在 70°C 下干燥（干燥）和干燥并过 2mm 筛子后粉碎。为了评估最佳扫描条件，我们制定了 PXRF 模型与 ICP 原子发射光谱法相关的性能指标。草皮和树皮样本的 PXRF 和 ICP 浓度最高（例如 Zn、Pb、Cd、Fe），但 K 和 Cl 除外。验证统计数据表明，PXRF 的稳定验证预测能力依次增加：干燥完整<现场湿润<干燥粉碎。即使在现场湿润条件下，也可以合理地使用 PXRF 来测定 Zn（决定系数，R 0.86；残差预测偏差，RPD 2.72）和 Cu（R 0.77；RPD 2.12），而干燥粉碎后的样本则允许对 Pb（R 0.90；RPD 3.29）、Fe（R 0.80；RPD 2.29）、Cd（R 0.75；RPD 2.07）和 Cu（R 0.98；RPD 8.53）进行稳定验证预测。总之，PXRF 是一种快速评估植被中元素浓度的有用方法。未来的 PXRF/植被研究应探索其他元素，并研究其在评估植物修复效果方面的有用性。
