Irini Papageorgiou*, Srimathie P. Indraratne, Darshani Kumaragamage, and Douglas M. Goltz
The University of Winnipeg, Winnipeg, MB, Canada R3B 2E9

Mining and smelting activities have resulted in widespread environmental contamination through the release of heavy metals and other pollutants into soils, water bodies, and the atmosphere of boreal forest soils with potentially toxic metals, including cadmium (Cd) and zinc (Zn). In Flin Flon, Manitoba, limestone has been commonly applied as a remediation amendment to reduce soil acidity and improve site conditions; however, its effectiveness for direct metal immobilization remains poorly understood. Biochar has emerged as a promising alternative due to its high surface area, alkalinity, and metal sorption capacity. This study evaluates the effectiveness of limestone, biochar, and a 1:1 biochar–limestone mixture for Cd and Zn immobilization under temperature conditions representative of boreal environments. Batch adsorption studies were conducted at 22°C and 4°C to evaluate Cd and Zn sorption kinetics, adsorption capacities, and the influence of temperature on amendment performance. Preliminary results from Cd kinetic studies indicate that adsorption was greater at 22°C than at 4°C for all amendments. Biochar exhibited the highest adsorption capacity and reached equilibrium rapidly, while the biochar–limestone mixture showed intermediate performance. Limestone displayed minimal Cd adsorption. These findings indicate that direct Cd retention is primarily associated with biochar rather than limestone. Ongoing work includes adsorption isotherm modeling for Cd and Zn, surface characterization of amendment–metal complexes, and incubation studies evaluating amendment performance in contaminated boreal (pH = 5) soils under contrasting temperature regimes. It is anticipated that the combined amendment will provide complementary benefits by coupling the metal adsorption properties of biochar with the pH-adjustment capacity of limestone. The results will improve understanding of amendment mechanisms and support the development of more effective remediation strategies for metal-contaminated boreal forest soils.