Biochar From Soybean Straw Reduces Heavy Metals Mobility in Contaminated Agricultural Soils While Enhances Its Quality

PARDO S. D.; BARBERO MEDINA G.P.; MEDINA, R.; SALAZAR M.J.; WANNAZ, E.D.; BLANCO A.

Montevideo

Congreso; SETAC Latin America 15th Biennial Meeting; 2023

Society of Environmental Toxicology and Chemistry

The use of biochar (BC) as an organic amendment to remediate soils contaminated with heavy metals (HMs) is projected as an efficient, profitable and ecological remediation tool, since it is obtained from residual organic matter and improves soil quality due to its capacity to immobilize HMs, improve physicalchemical properties and favor the development of microbiological communities. These properties depend on the BC production conditions and the raw material used.The aim of this work was to evaluate the effect of BCs produced at different temperatures on agricultural soils contaminated with HMs. For this purpose, BCs produced from soybean straw at 300 °C (BCI), 400 °C (BCII) and 500 °C (BCIII) were used. The contaminated agricultural soils (CAS) were collected in the vicinity of an open dump of industrial waste in the province of Córdoba, Argentina, and presented elevated concentrations of Pb, Cd, Cu and Zn. The collected soils were dried, homogenized and distributed in 7 treatments (n=8): Control; CAS with no BC; CAS amended with BCI; CAS amended with BCII; CAS amended with BCIII; Mixture; and Mixture amended with BCIII. The "mixture" treatments correspond to CAS soils with a 10 % addition of proximate soils which present a higher degree of contamination. This mixture was performed to simulate the future dispersion of the HMs. All the soils were incubated in darkness at 65% water-holding capacity with samples from each replicate being collected every 3 months.The response variables determined for all samples were: concentration of Pb, Cd, Zn and Cu in five soil fractions through sequential extraction (I, II, III, IV and V), with fractions I and II being Considered as bioavailable; soil physicochemical parameters (pH, electrical conductivity (EC), organic matter content (OM)); general microbiological activity by hydrolysis of Fluorescein Diacetate (FDA).The results revealed that BC application significantly reduced the HMs concentration in the bioavailable fractions compared to CAS and increased the physicochemical parameters (pH, EC, % soil OM and WRC). There were no significant differences among the treatments with different BCs. Microbiological activity was not affected by BCs application.With these results we can conclude that, in the short term, the use of BCs produced from soybean straw is efficient for HMs immobilization as well as for improving the physicochemical properties of agricultural soils.