## 1 Introduction
According to [PERSON] et al. [24], plant Cd and Pb accumulation are influenced by many factors, such as soil pH, organic matter content, and soil metal concentration. A direct measurement of soil quality is impossible due to the wide range of integrating factors associated with various soil usages [19]. Metal contamination in soil is now a significant issue on a global scale [25]. Given their influence on the concentration and bioavailability of toxic elements, humic compounds and soil texture were chosen as this study's primary areas of attention. As major constituents of soil organic matter, humic compounds like FAs and HAs can have big effects on the movements and behaviours of toxic soil elements. The availability of heavy metals to plants and other living things can be greatly influenced by their capacity to bind and mobilise them. Additionally, the amounts of clay, silt, and sand in the soil affect not only the physical and chemical characteristics of the soil, but also its ability to bind and release heavy metals. Variations in soil texture-related parameters such as porosity, wetness, and others can have an impact on metal availability to plants and microorganisms. UV-Vis spectroscopy can determine the colour quotients of humic substances, which are used to measure the quality of humus in soil. Additionally, the impacts of changes in land usage on the composition and structure of humic substances have been noted, emphasising the dynamic nature of soil properties and humus composition. The advantage of a spectrophotometric determination of the colour quotient is that there is no need to extract the constituent fractions of humic substances (HSs) [26]. The absorbance at a wavelength of 465 nm corresponds to the absorption of the radiation of young humic substances at an early stage of the humification process. The value of the absorbance at 665 nm wavelength is indicative of how much radiation is absorbed by mature, well-humified humic compounds. The degrees of condensation, dispersion, and maturity of humic compounds are indicated by their colour quotients [27]. As the molecular weight and condensation degree increase, the value coefficient of Q4/6's humification falls. The small colour quotient ratio indicates older, humidified organic material with a large concentration of condensed, and hence aromatic, chemicals. On the other hand, a high value of \(Q4/6\) suggests a low degree of aromatic condensation but also indicates a higher proportion of aliphatic compounds and is typical for new, small-scale humidified humic acid that has just been supplied with organic materials. Studies on the chemical characteristics of humic acids, their combination of elements, and the content of carboxyl, aliphatic, and aromatic groups accurately characterise the stability of humic substances and humification degree of soil organic matter [28]. For the purpose of conducting a thorough assessment of the effects on soil fertility, it is imperative that the reactions of soil parameters, such as _TOC_, pH, etc., be thoroughly studied [1]. The aim was to characterise the sorption of heavy metals (Cd and Pb) in Andosol, Cambisol, and Planosol in specific soil types of neovulcanites from the Kremnicke vrchy Mountains in Slovakia by identifying the kinds and amounts of humic compounds in the soil, as well as the characteristics of the textures of the soil types. This research was oriented toward the interactions between soil properties, humic substances, and heavy metal sorption, especially in diverse geological and environmental conditions. By focusing on the specific soil types and selected regions in Slovakia, this study aimed to provide insights into the relationships between soil composition, HSs, and the sorption of toxic elements. Significant changes in soil properties can result from both natural and human-caused management.