# Characterisation of Dust Particles Deposited on Photovoltaic Panels in the United Arab Emirates
## 3 Results and Discussion
### Dust Chemical Composition (XRD Characterisation)  
X-ray diffraction (XRD) was employed to determine the chemical composition and crystal structure of materials, including dust particles. The XRD methodology for determining chemical composition begins with the preparation of the sample. The material of interest is finely ground into a powder and then typically pressed into a thin disc or mounted on a sample holder. X-rays are emitted from a source and directed onto the sample. When these X-rays interact with the crystal lattice of the sample, they undergo diffraction, producing a distinct diffraction pattern on a detector. The collected data, consisting of angles and intensities of the diffracted X-rays, are then analysed to identify crystallographic planes and the arrangement of atoms in the crystal lattice. This information is crucial for determining the phases present in the sample. The diffraction pattern is often compared to a database of known crystal structures to aid in phase identification. Quantitative analysis can be performed by examining the intensities of the diffraction peaks, allowing for the determination of the relative amounts of different phases. While XRD provides insights into the crystal structure and phases, it is often complemented by other techniques, such as Elemental Composition Analysis via EDS, to achieve a more comprehensive understanding of the material's chemical composition. For the current analyses, the investigation into the structural properties of the collected samples was conducted with precision using an X-ray diffractometer employing Cu K\(\alpha\) radiation (\(\lambda\) = 1.54 A). The meticulous diffraction pattern acquisition was executed under specific conditions: a tube current of 30 mA and a target  
Figure 1: Optical images of the dust from five different PV installation sites. voltage of 40 kV. The scanning parameters, encompassing a range of 20 values from 5\({}^{\circ}\) to 70\({}^{\circ}\) (20) min\({}^{-1}\), were calibrated with a scan speed of 2\({}^{\circ}\) (20) min\({}^{-1}\) to ensure comprehensive coverage of all significant diffraction peaks. Identification of XRD diffraction peaks for the collected solids was based on a rigorous adherence to the theoretical intensity of the three most eminent peaks characterising the respective minerals in their pure state [20; 21]. Figure 2 shows the XRD patterns for the five dust samples. Figure 3 shows the outcomes of the XRD analysis conducted on these samples collected from the mentioned geographical locations. Based on the XRD characterisation results, the dust samples collected from the five locations have different chemical compositions. The XRD analysis depicted in Figure 2 affirms the ubiquity of calcium carbonate (calcite) across all samples, substantiated by the intensity of the most distinguished peak associated with calcium carbonate minerals in their pure state. Silica (SiO\({}_{2}\)) was consistently observed in all samples, except S-10. The presence of dolomite (CaMg(CO\({}_{3}\))) in samples S-10, GT-10, and GS-10 is noteworthy, whereas titanium oxide (TiO\({}_{2}\)) was selectively confirmed solely in samples GT-10 and GS-10. Sulphate components, exemplified by Anhydrite (or Gypsum), were exclusively located in sample R-10, and the presence of Hypermangan (KMnF\({}_{4}\)) was discerned in a singular sample, namely S-10. The minimal composition observed in sample T-10, characterised by the exclusive presence of calcium carbonate and trioxidosilicate components, is of significance. Conversely, samples GS-10 and GT-10 exhibited a diversified array of components, as evidenced by the intricate patterns observed in the XRD analyses. The results in Figure 3 confirm the presence of diversity of the phases across different locations even though the dust was collected from the PV surface which provides a point of departure from the Optical Microscopy results.