# Effect of Particle Size on Composet Analysis by Portable X-ray Fluorescence
## 3 Results and Discussion
### Effect of the Sample Grinding on the Elemental Concentration Determined by pXRF
\begin{table}
\begin{tabular}{l l c c c c c c c} \hline
**Element** & **Compost** & \multicolumn{2}{c}{**Whole Sample**} & **Element** & **Compost** & & & \\ \hline  & & **Unground** & **Sig. 1** & **Ground** & & & **Unground** & **Sig. 1** & **Ground** \\ \hline  & Sewage & 30.6 & * & 32.3 & & Sewage & 20.1 & ns & 20.3 \\ Rb & MSW & 16.2 & ns & 17.5 & \(\mathrm{S}\times 10^{-3}\) & MSW & 9.81 & ns & 9.13 \\  & Alperujo & 14.8 & ns & 14.5 & & Alperujo & 3.85 & ns & 3.51 \\ \hline  & Sewage & 99.0 & * & 114.6 & & Sewage & 10.4 & ns & 10.9 \\ Zr & MSW & 45.8 & ns & 59.7 & \(\mathrm{K}\times 10^{-3}\) & MSW & 18.1 & ns & 18.3 \\  & Alperujo & 39.7 & ns & 35.9 & & Alperujo & 45.3 & ns & 46.6 \\ \hline  & Sewage & 155 & ns & 151 & & Sewage & 13.9 & * & 14.3 \\  & MSW & 156 & ns & 204 & \({}^{2}\) P \(\times\) 10\({}^{-3}\) & MSW & 5.95 & ** & 7.02 \\  & Alperujo & 71.4 & ns & 68.9 & & Alperujo & 1.99 & ns & 1.89 \\ \hline  & Sewage & 464 & ns & 451 & & Sewage & 108 & ns & 112 \\ Zn & MSW & 652 & * & 536 & \({}^{2}\) Si \(\times\) 10\({}^{-3}\) & MSW & 42.5 & ns & 46.1 \\  & Alperujo & 28.7 & * & 24.0 & & Alperujo & 27.4 & ns & 31.8 \\ \hline  & Sewage & 177 & * & 167 & & Sewage & ND & & ND \\ Cu & MSW & 248 & ** & 185 & \({}^{2}\) Cl \(\times\) 10\({}^{-3}\) & MSW & ND & & ND \\  & Alperujo & 71.2 & ns & 62.2 & & Alperujo & 1.56 & ns & 1.55 \\ \hline  & Sewage & 38.0 & ns & 37.1 & & Sewage & 14.9 & ns & 16.6 \\ Pb & MSW & 81.2 & ns & 82.2 & \({}^{2}\) Al \(\times\) 10\({}^{-3}\) & MSW & 8.02 & ns & 7.58 \\  & Alperujo & ND & & ND & & Alperujo & 3.76 & * & 4.47 \\ \hline  & Sewage & 376 & ns & 426 & & Sewage & 51.6 & ns & 50.4 \\ Mn & MSW & 140 & ns & 171 & \({}^{2}\) Fe \(\times\) 10\({}^{-3}\) & MSW & 27.1 & ns & 26.3 \\  & Alperujo & ND & & ND & & Alperujo & 5.02 & ns & 4.92 \\ \hline  & Sewage & 12.7 & ns & 12.2 & & Sewage & 48.3 & ns & 48.7 \\ As & MSW & ND & & ND & \({}^{2}\) Ca \(\times\) 10\({}^{-3}\) & MSW & 98.3 & ns & 100.3 \\  & Alperujo & ND & & ND & & Alperujo & 57.2 & ns & 58.0 \\ \hline  & Sewage & 69.5 & ns & 79.3 & & & Sewage & 715 & ns & 704 \\ V & MSW & ND & & ND & \({}^{2}\) Bal \(\times\) 10\({}^{-3}\) & MSW & 774 & ns & 774 \\  & Alperujo & ND & & ND & & Alperujo & 875 & ns & 871 \\ \hline  & Sewage & 2478 & ns & 2498 & & & & & \\ Ti & MSW & 1100 & ns & 1067 & & & & & \\  & Alperujo & 634 & ns & 764 & & & & \\ \hline  & & & & & & & & & \\ \end{tabular}  
* \({}^{1}\) ns: Non-significant difference.
* \(p<\) 0.05, *
* \(p<\) 0.01; \({}^{2}\) For these elements, measurements were conducted in the precalibrated mining mode; for the rest of the elements, the measurements were performed with the precalibrated soil method.  
\end{table} 
Table 4: Effect of sample grinding on the pXRF elemental readings in integral compost samples (comparison by \(t\)-test in three paired replicates). the MSW compost, the results were higher in the ground fractions for the elements Si, P, and Pb. In addition, in the alperujo compost, differences were observed for the Si, K, and Ti concentrations. The attenuation of the X-rays within the individual coarse particles is known as the particle size effect. This effect is more pronounced for light elements (Z \(<\) 20), among which would be elements such as Al, Si, P, and K [26]. However, signal attenuation in coarse, unground particles was also observed in this study for other elements with Z \(>\) 20. The elements Ti, Sr, and Zr were more abundant in the soil, while they were found in reduced concentrations below 100 mg kg\({}^{-1}\) in the plant material [22; 27]; therefore, the increases in the concentration readings found for them when grinding must be related to the mineral fraction of the composts before their organic fraction. Although the compost samples were homogenized before being placed in the measuring cup, it was possible for the fine and dense soil particles to settle in the porous medium constituted by the coarse particles of the plant material, thus escaping from the X-ray beam. In this way, possibly, the increases in