Application of biochar amendments for enhancing the quality of agricultural soils contaminated with heavy metals.

PARDO, SHEILA DANIELA; BLANCO, ANDRÉS; BARBERO MEDINA, GONZALO PEDRO; PANETTIERI MARCO; CÉSAR PLAZA; MERILES JOSE; WANNAZ, E.D; SALAZAR, MARIA JULIETA

pisa

Conferencia; 13th conference of SUITMA (Soils of Urban, Industrial, Traffic, Mining and Military Areas); 2025

Biochar (BC), a material produced by biomass pyrolysis, emerges as a promisingstrategy for the remediation of heavy metal (HM) contaminated soils throughimmobilization, improving their physicochemical and microbiological properties,increasing their productive quality, and capturing carbon. Our objective was to determinethe effect of BCs produced from soybean straw pyrolyzed at 300 °C (BCI), 400 °C (BCII),and 500 °C (BCIII) on the immobilization of HMs in agricultural soils contaminated withPb, Cd, Cu, and Zn (SAC) and on soil quality. The SAC were collected near an open-airlandfill of industrial waste in an urban area in Córdoba, Argentina. Subsequently, theywere distributed into 4 treatments (n=8): SAC; SAC with BCI; SAC with BCII; and SACwith BCIII. They were incubated for one year in darkness at 65% of water holdingcapacity. Afterward, a complete soybean cultivation cycle was carried out, and thefollowing variables were determined at the beginning and at the end of the incubationand post-harvest: HM mobility (Tessier sequential extractions), total carbon (C) andnitrogen (N), BC stability (TGA), soil aggregate stability, and microbial activity (FDA,dehydrogenase, glucosidase). The study revealed that the concentration of the four HMwas significantly reduced in the bioavailable fraction across all BC treatments,throughout both incubation and cultivation. Furthermore, TGA demonstrated a directrelationship between BC stability and its production temperature. Interestingly, while soilaggregate stability improved in all treatments over the course of the incubation andcultivation processes, BC did not influence this variable. However, BC amendment didsignificantly increase the total carbon content in the soil by 3.5 to 4 times and the totalnitrogen content by 1.6 to 1.8 times. A slight decrease in both nitrogen and carbon wasobserved during the incubation period across all biochar treatments, with no furtherchanges detected after cultivation. Importantly, the application of biochars led to anenhancement in the activity of soil microorganisms. These results demonstrate theefficiency of BC to immobilize HMs and improve the quality of agricultural soils regardlessof the production temperature, positioning it as a potentially efficient and sustainableremediation technology.