## 1 Introduction  
Soil contamination with trace elements (TE) is a common problem in terrestrial ecosystems as a result of their dispersion. It is related to urbanization and industrial activities, such as mine tailings, disposal of high metal wastes, leaded gasoline and paints, the application of fertilizers to land, animal manure, sewage sludge, pesticides, wastewater irrigation,coal combustion residues, the spillage of petrochemicals, and others [1; 2; 3]. TE cover a group of inorganic elements, including potentially hazardous metals commonly found at contaminated sites in concentrations exceeding their permissible contents [4; 5; 6]. Although the presence of TE in soil originates from parent-rock material, TE might be converted to mobile forms due to changes in environmental conditions or soil properties. Their mobile forms may be available to living organisms [7]. The bioavailability of TE in soils is considered a dynamic process comprising three distinct steps: (1) environmental availability, i.e., the total amount of TE in the soil, including both actual and potential fractions, which can be dissolved from the soil matrix into the pore water; (2) environmental bioavailability, i.e., the amount of dissolved fraction in the pore water that can be taken up by plant roots or other soil organisms; and (3) toxicological bioavailability, i.e., the amount of TE that can physiologically induce bioaccumulation or other effects within plants depending on translocation, metabolism, and degradation [3; 8; 9; 10]. All these approaches to bioavailability are strongly affected by soil physicochemical properties [3; 7; 10; 11; 12; 13]. Soil components imply the sorption processes and control TE behavior because soils differ greatly in their sorption capacity, their cation and anion exchange ability, and the binding energies of their sorption sites. The sorption of metals in soil may be very fast (from 5 to 15 s), but the kinetic rates depend on the properties of the TE [11]. The strength of metal binding and retention may be additionally caused by many other soil factors, such as pH, the nature of the soil's components, the presence and concentration of organic and inorganic ligands, root exudates, and nutrient concentrations [2; 3; 10; 11; 14; 15]. Among different remediation approaches, in situ and ex situ processes, including excavation, solidification, stabilization, soil washing, electroremediation, and phytoremediation, have been used to mitigate the negative impact of metals in soils [2; 15; 16; 17; 18]. To achieve effective reductions in the TE availability in soil, various amendments are proposed in the scientific literature [2; 14; 15; 17; 19; 20; 21]. Chemical stabilization is a valuable strategy for a wide range of contaminated sites. TE stabilization can be carried out using materials of organic and inorganic origin characterized by diversified sorption affinity and influence on soil properties [2]. The application of inorganic soil stabilizers, including lime, phosphate materials, zeolite, bentonite, septic, or Fe/Mn oxides, is based on their ability to shift soil pH, precipitate insoluble TE minerals, occlude TE, or enhance their binding, thus leading to a longer-lasting remediation effect [2; 10; 17; 22; 23]. Organic materials, such as biosolids, composts, manure [14; 15; 16; 18; 19; 20], and biochar [20], have attracted significant attention from researchers as potential high-performance materials due to their considerable sorption affinity with a wide range of soil contaminants. The search for the most effective soil amendment is ongoing due to the high potential for the immobilization of TE in the soil and the associated low risk of releasing metals during their aging processes. The recovery of contaminated soils in highly polluted areas is necessary to prevent the deterioration of the environment, as well as to control the exposure to hazardous and toxic compounds for humans and other living organisms.