## 3 Results and Discussion
### Carbon Parameters
The main elements of soil organic matter are HSs, which include FAs and HAs [55]. They are essential in soil structure, nutrient retention, and the complexation of toxic elements. The contents of _HS_, _HA_, and _FA_ in the soil profiles provide valuable information about the quality and composition of organic matter, influencing soil fertility and the availability of essential nutrients for plant growth [45]. The TOC and other organic materials reduced as soil depth increased, which agrees with the claim of [PERSON] et al. [50]. The TOC content in the Cambisol soil type (P1, P2, P4) ranged from 0.13% to 5.37%, and the average value for the soil types studied was 1.530%. The averaged value for Andosol (P3) was 7.432%, and that for the Planosol soil type (P5) had a value of 2.653% (Table 2). Figure 2 provides a comprehensive overview of the carbon parameters in soil profiles, colour quotient of humic substances (\(Q_{HS}\)), colour quotient of humic acids (QHA), colour quotient of fulvic acids (QFA), and the humification degree (DH). These parameters are essential for understanding the composition and quality of organic matter in the soil. In the Cambisol and Planosol soils, there is a higher concentration of condensed compounds and an increased level of humification, as shown by the measured values of the colour quotient of humic substances. There was no discernible variation in the colour values of the humic substance quotient among these two categories of soil. The average values of the detected humic substances' colour quotient in Cambisol were lower (in the range from 2.36 to 2.71) than that in Planosol (\(Q_{HS}\) = 3.10). The greatest average value of the colour quotient was found in the P3 profile (the Andosol in the xerothermic meadow), with varied degrees of organic matter decomposition on the soil's surface and a steady supply of dead plant material generating the underlying organic horizon. The low-humified HAs that were supplied with a new source of organic materials had a greater colour quotient. The use of land resources has an impact on the amount of soil HSs. Since the absorbance at 465 nm, which is typical for these young humic compounds, was greatest for Andosol, the UV-Visspectrum indicates that the Andosol soil observed in profile P3 had numerous juvenile humic substances at the very beginning of humification. Figure 2 shows that the colour quotient values for HAs ranged from 2.08 to 5.97, while those for FAs ranged from 5.66 to 13.84. The present findings are consistent with those of [PERSON] and [PERSON] [27]. Planosol from a moved meadow showed the greatest levels of humification, the concentration of the aromatic core, and as a result, the humic compounds' quality (Figure 2). Profile P3 had the least amount of humification that we could find with the new availability of organic matter and the greatest amount of _TOC_ and HSs (Table 2, Figure 2). As a result, the smaller degrees of humic material dispersal and condensate, the lower the contents of the bioavailability forms of selected metals. The principal functional groups in humic materials include carboxylic acid, phenolic and alcoholic hydroxyl, ketone, and quinone groups. Alkyl/aromatic units form the backbone of humic compounds, which are mostly cross-linked by the presence of nitrogen and oxygen [56]. [PERSON] et al. [57] stated that the functional groups that contain oxygen found in humic and fulvic acids, such as carboxylic, phenolic, and carbonylic groups, are primarily responsible for their capacity to complex. Chelate compounds are particularly significant. As ligands, the fulvic and humic functional groups are involved. Each of the groups has the ability to build closed rings by occupying two or more coordinating places around metal ions. Particularly on volcanic substrate, the humic substances of Andosol were distinguished by a significant level of humification. A larger ratio of _c(HK):c(FK)_ is linked to greater humification characteristics of HSs (Figure 2).