The heavy metal contamination of soils is a global environmental challenge threatening water quality, food safety, and human health. Using a systematic literature review approach, this study aimed to assess the potential of bacterial strains to immobilize cadmium (Cd²⁺), lead (Pb²⁺), and copper (Cu²⁺) in contaminated soils. A total of 45 articles were analyzed, focusing on studies that reported heavy metal concentrations before and after bacterial treatment. The analysis revealed that bacterial genera such as Bacillus, Pseudomonas, and Enterobacter were most commonly used for the immobilization of these metals. Immobilization efficiencies ranged from 25% to over 98%, with higher efficiencies generally observed when microbial consortia or amendments (e.g., phosphate compounds and biochar) were applied. The main immobilization mechanisms included biosorption, bioprecipitation (such as carbonate-induced precipitation), bioaccumulation, and biomineralization, which convert mobile metal ions into more stable, less bioavailable forms. These findings highlight the promising role of microbial-assisted immobilization in mitigating heavy metal pollution and reducing ecological risks. Further laboratory and field studies are needed to optimize the use of these microbial strains under site-specific conditions to ensure effective and sustainable soil remediation practices.

Soil contamination by heavy metals poses a significant threat to the environment and human health, primarily due to the toxicity of these metals and their ability to accumulate in organisms. To determine how soil pH and temperature affect the chemical speciation, mobility, and immobilization potential of cadmium (Cd²⁺), lead (Pb²⁺), and copper (Cu²⁺). The main hypothesis posits that as pH increases, the concentration of free heavy metals decreases due to the formation of complexes and precipitation, whereas an increase in temperature accelerates the kinetics of chemical reactions, thereby altering metal activity. Using the Visual MINTEQ modeling tool, simulations were carried out under various pH (4–8) and temperature (15–40 °C) conditions. The results showed that at lower pH, metal activity significantly increases; however, the influence of temperature is more complex–both positive and negative trends were observed depending on the metal. These findings provide a foundation for further research, particularly for optimizing strategies to immobilize contaminated soils. Nonetheless, certain observed trends diverged from initial assumptions and called for additional investigation.

Scientists state that in recent years, the level of soil contamination worldwide has significantly increased, mainly due to atmospheric deposits, floods, agricultural and industrial activities, and mining. Soil contamination is a widespread issue that negatively impacts the functions and processes of soil microorganisms. This pollution is associated with disrupting the physiological functions of microorganisms and disrupting processes related to the decomposition and transformation of organic matter. Heavy metals are significant factors of soil pollution, posing a threat to ecosystem functions due to their toxicity, persistence, and ability to bioaccumulate. The soil hosts diverse communities of microorganisms with specific metabolic capacities. Some microorganisms contribute to the decomposition of organic matter by interacting with toxic metals, while others participate in the formation of natural nanoparticles, thereby reducing the toxicity of heavy metals. Microorganisms can be used to immobilize heavy metals, but their effectiveness depends on various parameters such as soil type, chemical composition, pH, temperature, and moisture. The study identified suitable conditions that can stimulate the growth and activity of microorganisms. Optimal temperature is essential for the metabolic processes of microorganisms, such as enzyme activity, pollutant degradation, and biomass growth. Too low pH can inhibit the growth and enzyme activity of microorganisms, while too high pH slows down their activity. The article discusses that although microorganisms can be used in bioremediation, their activity is influenced by soil parameters. Understanding microorganisms` properties and operational parameters is essential for their successful application in soil bioremediation processes. However, this requires delving into not only the complexity of ecosystems, the impact of pollutants, and environmental parameters. The targeted application of microorganisms in bioremediation could become one of the main solutions for combating soil contamination and achieving environmental sustainability.