## 3 Results and Discussion
### Mineralogical and Microstructural Analyses of Soil
The values include a more intense absorption band, centered around 1433 cm\({}^{-1}\), attributed to the C-O group's asymmetric stretching vibration, and two narrower bands centered at 874 cm\({}^{-1}\) and 712 cm\({}^{-1}\), characteristic of the same group's deformation vibration. The ATR-FTIR spectra of the studied soil samples also highlight the presence of dolomite through the maximum peak centered at 1433 cm\({}^{-1}\), attributed to the asymmetric stretching vibration of the CO3- ion [82], present in the chemical composition of this mineral (Ca Mg(CO3)2). The intensity of the peaks associated with the characteristic absorption bands of calcite at 1433 cm\({}^{-1}\) and 874 cm\({}^{-1}\) (Figure 7) is directly proportional to the percentage of CaCO3 in the soil. The very low organic carbon percentages correlate with the absence of peaks in the ATR-FTIR spectrum. Specifically, the peaks at 2920-2926 cm\({}^{-1}\) and 2850-2852 cm\({}^{-1}\), which are indicative of the symmetric and antisymmetric stretching vibrations of the functional group CH2[79; 81], are absent. The ATR-FTIR spectra of the soils examined in this study closely resemble those obtained by [83] for soils collected from parks located in the city of Galati, confirming the mineralogical footprint of the region. The SEM-EDX technique was very valuable for examining the mineralogy of the soil and providing a semi-quantitative analysis of its elemental composition (Figure A1, Appendix A). Additionally, the results from SEM-EDX mapping (Figure A1, Appendix A) confirmed the findings obtained through the ATR-FTIR method. The analysis indicates a consistent elemental composition across the studied soils in the Lower Danube Basin. The SEM-EDX semi-quantitative results (Appendix A, Table A1) revealed the distribution of major and trace element content in agricultural soils, as shown in Figure 9.  
The concentrations of O and Si were the highest among the 24 identified elements. (Appendix A, Table A1). Notably, the O level in soil is lower compared to the value of this element in Earth's crust (46%) [84]. Silicon, a trace element present in plants and soils, exhibits variable concentrations across different soils and plant species. It constitutes 65.4% (SiO2) of the upper layer of European soils [63] and accounts for 27% of the Earth's crust [84]. Silicon plays a crucial role in promoting plant growth and influencing the availability and accumulation of both macro- and micronutrients [85]. In soil, silicon exists in both liquid and solid states, with the solid form being either amorphous (derived from the parent rock or living organisms) or crystalline (present in primary and secondary silicates and silicate materials) [86]. The presence of silicon in soil samples is validated using the ATR-FTIR method, which identifies the absorption bands characteristic of the chemical bonds formed by silicon with other elements in the soil's clay and non-clay minerals. In the analyzed samples, varying concentrations of alkaline elements (sodium, magnesium, potassium, and calcium) were found (Appendix A, Table A1). The alkaline metals content in the Earth's crust is in the following order: Ca (5.0%) > Mg (2.9%) > Na (2.3%) > K (1.5%) [84].