Experimental Investigation of Cadmium, Lead, and Copper Immobilization in Soil Using Priestia sp. J4

Soil contamination with heavy metals poses a significant threat to the environment and human health due to their toxicity, mobility, and ability to accumulate in the food chain. The aim of this study was to evaluate the ability of Priestia sp. J4 to reduce the mobile fractions of cadmium (Cd2+), lead (Pb2+), and copper (Cu2+) in soil. Sterilized soil artificially contaminated with Cd2+, Pb2+, and Cu2+ salts was used in the experiment. The microorganism was applied at three concentrations: 3.20 × 1011, 1.92 × 1011, and 1.28 × 1011 CFU. Soil samples were incubated at 30°C for 12 weeks. Concentrations of the mobile fractions of heavy metals were determined using 0.01 M CaCl2 extraction followed by ICP-OES analysis. The results demonstrated that Priestia sp. J4 reduced the mobility of all investigated metals. At the lowest measured CaCl2-extractable concentrations, the non-extractable proportions relative to the total metal concentrations reached 99.9% for cadmium, 99.8% for lead, and 96.8% for copper. The lowest CaCl2-extractable concentrations of Cd2+ was observed during weeks 8–10, with Pb2+ showing low concentrations already during week 7, whereas the lowest CaCl2-extractable Cu2+ concentration was recorded in week 10. These findings indicate that Priestia sp. J4 is a promising microorganism for reducing the mobility of Cd2+, Pb2+, and Cu2+ in contaminated soils.