Several of the lighter main elements showed the largest variation between wet and dry, including phosphorus, sulphur, calcium, iron, and potassium (Table 1 and 2). The kangaroo paw has less variation between the data from wet to dry, however, the calcium value for the dry sample is considerably higher than the wet.
The presence of moisture cause the systematic under reporting of elements. This may be a result of the water molecules diffracting the incident energy, reducing the amount that interacts with the soil sample and is subsequently detected by the XRF instrument (Wines H, Luther J., 2018).
In conclusion, moisture in XRF samples can have a significant impact on the quality of the data. Therefore, it is an important to collect dry samples or to dry samples prior to analysis to obtain reliable results.
For more information, please refer to:
Wines H, Luther J., The Effects of Moisture on X-Ray Fluorescence Spectrometry, James Madison University, Available at: https://justjournal.org/2019/02/10/soil-moisture-effects-on-portable-x-ray-fluorescence-spectroscopy-and-visible-near-infrared-spectroscopy-measurements/ [Accessed 1 June 2020]