## 3 Results and Discussion
### Mineralogical and Microstructural Analyses of Soil  
Soils encompass a complex array of chemical components, comprising both mineral factions such as clays, oxides, and quartz as well as organic fractions constituted by organic matter in various stages of decomposition. Additionally, soils contain water and air. The intricate composition of soils renders them a challenging material to study, requiring a comprehensive approach that considers the interplay of the various components. Based on the soil ATR-FTIR spectra featured in Figure 7, it is evident that the absorption bands of the analyzed soil samples share similarities, but their peak intensities differ. This indicates the presence of various functional groups of chemical elements, which are characteristic of both clay minerals and non-clay minerals. Within the spectral range of 1500-400 cm\({}^{-1}\), known as the \"spectral fingerprint domain\" [73], distinctive absorption bands of clay minerals including montmorillonite ((Na,Ca)\({}_{0.33}\)(Al,Mg)\({}_{2}\)(Si\({}_{4}\)O\({}_{10}\))(OH)\({}_{2}\)\(\cdot\)nH\({}_{2}\)O) and kaolinite (Al\({}_{2}\)Si\({}_{2}\)O\({}_{5}\)(OH)\({}_{4}\)) were identified. Additionally, non-clay minerals such as quartz (SiO\({}_{2}\)), feldspars (orthose (KAlSi\({}_{3}\)O\({}_{8}\)), albite (NaAlSi\({}_{3}\)O\({}_{8}\))), and calcite (CaCO\({}_{3}\)) were also recognized. Table 5 displays the ATR-FTIR peaks that represent the functional groups associated with the primary minerals present in the studied soils. To emphasize the absorption bands in the 850-1250 cm\({}^{-1}\) range, the ATR-FTIR spectra were deconvoluted, as illustrated in Figure 8[74]. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Mineral Type** & **Absorption Band** & **Band** & **References** \\
**(cm\({}^{-1}\))** & **Assignment 1** & & \\ \hline _Cluy minerals_ & & & \\ \hline \multirow{6}{*}{Montmorillonite} & 830 & \(\beta\)(_AI-OH-Mg)_ & 840–830 cm\({}^{-1}\)\(\beta\)(AI-OH-Mg) [75] \\  & 912 & \(\beta\)(_AI-AI-OH_) & 930–910 cm\({}^{-1}\)\(\beta\)(OH) [75] \\  & 1633 & \(\beta\)(_OH_) & 1635 cm\({}^{-1}\)\(\beta\)(OH) [78] \\  & 3390 & \(\
u\)(_OH_) & 3392 cm\({}^{-1}\)[79] \\  & 3700–3600 cm\({}^{-1}\) inner surface v(OH) & 3610–3621 cm\({}^{-1}\) abnormal montmorillonite [80] \\  & 3620 & _inner surface_ & 3620 cm\({}^{-1}\) v(OH) [75] \\  & & & 3627 cm\({}^{-1}\)[79] \\ \hline \multirow{6}{*}{Kaolinite} & 419 & \(\beta\)(_Si-O-Si_) & 430–420 cm\({}^{-1}\)\(\beta\)(Si-O) [75] \\  & 912 & \(\beta\)(_AI-OH-Al_) & 930–910 cm\({}^{-1}\)\(\beta\)(OH) [75] \\  & 915 cm\({}^{-1}\)\(\beta\)(OH) [76–78] \\  & 1032 & \(\
u_{\rm u}\)(_Si-O-Si_) & 1037 cm\({}^{-1}\)\(\
u_{\rm u}\)(Al-O) [75] \\  & 1038 cm\({}^{-1}\)\(\
u_{\rm u}\)(Si-O-Si) [76] \\  & 3620 & _inner v(OH)_ & 3620 cm\({}^{-1}\) v(OH) [75–78] \\  & 3695 & _inner surface_ & 3690–  
The selected soil samples were found to contain montmorillonite and kaolinite minerals from the category of clay minerals. The stretching vibrations of the hydroxyl functional group (-OH) were attributed to these domains within the limits of 3390-3620 cm\({}^{-1}\) and 3620-3695 cm\({}^{-1}\), respectively. Reference [80] mentioned that the values of wave numbers in the range 3610-3621 cm\({}^{-1}\) are characteristic of abnormal montmorillonite, a category of mineral widespread in most soils, which presents a single dehydration reaction, while [76] reported that in the case of abnormal montmorillonite, the stretching vibration of the -OH group is highlighted by the peak with the value 3625 cm\({}^{-1}\). In the case of kaolinite, the asymmetric stretching vibration of the Si-O-Si group in the 1032 cm\({}^{-1}\) area was noticeable. The bending vibrations attributed to functional groups Al-OH-Al (912 cm\({}^{-1}\)), Al-OH-Mg (830 cm\({}^{-1}\)), and Si-O-Si (419 cm\({}^{-1}\)) were recorded in the 1000-400 cm\({}^{-1}\) area from the structure of clay minerals.