Impact of Biochar Particle Size on Heavy Metal Immobilization and Microbial Biomass Carbon in Contaminated Mining Soils

Advances in Agriculture and Agricultural Sciences | Vol. 12, No. 2, February 2026 | pp. 28–32

DOI: 10.46882/2026.AAAS.120206

Short Communication

Title: Impact of Biochar Particle Size on Heavy Metal Immobilization and Microbial Biomass Carbon in Contaminated Mining Soils

Names of Authors: Nguyen, T. V.¹, Nguyen, M. H.¹, and Kim, S. J.²

Authors’ Affiliations: ¹Department of Environmental Sciences, Vietnam National University, Hanoi, Vietnam. ²Department of Agricultural Biotechnology, Seoul National University, Seoul, South Korea.

Abstract: Heavy metal toxicity restricts agro-ecological restoration around legacy mining fields. This research investigated how varying the particle size of rice husk biochar (fine: less than 0.5 mm, medium: 0.5–2.0 mm, coarse: greater than 2.0 mm) influences cadmium (Cd) and lead (Pb) bioavailability, along with soil microbial biomass carbon (MBC). Biochar applications were fixed at a 2.5% weight ratio into multi-metal contaminated soils. Fine particle fractions reduced extractable Cd and Pb concentrations by 54.2% and 68.7% respectively, outperforming coarse variants. The expanded surface area of the fine biochar facilitated superior surface complexation and ion-exchange interactions. Concurrently, soil MBC increased from 112 mg/kg in untreated fields to 245 mg/kg within fine fraction environments after 60 days of incubation. Soil basal respiration rates steadied, confirming minimized toxicological inhibition of localized microflora. Enzymatic diagnostics revealed a 40.5% boost in dehydrogenase activities, showing improved biological functional status. These findings demonstrate that adjusting the physical dimensions of pyrolyzed organic amendments can accelerate the rehabilitation of polluted agricultural zones.

Keywords: Soil remediation; Pyrolysis footprint; Cadmium binding; Soil enzymes; Bioavailable fractions; Heavy metals.

Manuscript Timeline: Received October 30, 2025; Revised December 22, 2025; Accepted January 22, 2026; Published February 25, 2026.

Citation: Nguyen, T. V., Nguyen, M. H., and Kim, S. J. (2026). Impact of Biochar Particle Size on Heavy Metal Immobilization and Microbial Biomass Carbon in Contaminated Mining Soils. Advances in Agriculture and Agricultural Sciences, 12(2), pp. 28–32.

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