Abstract Biochar as a soil remediation product does not always produce a promising result. In a number of studies, this is explained by the nature and properties of biochar. The dependence of the efficacy of biochar application on the level of chemical pollution and soil properties has not been sufficiently studied. The study aimed to evaluate the effects of biochar in case of heavy polymetallic contamination of agricultural sandy podzolic soils (Albic Glossic Retisols (Loamic, Aric Cutanic, Ochric) with different levels of humus content using the ecotoxicological and microbiological parameters. Soils with different organic carbon contents (S1 with Corg 3.86 and S2 with 1.30%) were sampled at two sites (Moscow oblast). It has been experimentally proven that the efficiency of biochar application depends on both the humus status of the soil and the level of chemical pollution. The soils were intentionally contaminated with elevated levels of copper (Cu), zinc (Zn), and lead (Pb) at concentrations five and ten times higher than the Approximate Allowable Concentrations (AAC) for each metal (AAC—Cu: 132 mg/kg, Zn: 130 mg/kg, Pb: 220 mg/kg according to the standard accepted in Russia). The application of biochar effectively mitigated the ecotoxicity induced by the heavy metals in the low humus soil—Corg 1.30% (S2) at the 5 AAC concentration. Specifically, we observed a 25% increase in plant root length, and a 54% rise in root biomass. However, at 10 AAC the heavy metals completely inhibited these test responses. Interestingly, in the highly humified soil—Corg 3.86%, (S1), application biochar did not result in significant improvements in the ecotoxicological and microbiological parameters, regardless of the contamination dose. A significant positive impact of biochar on the functional activity of the soil microorganisms was observed exclusively in soil S2. Under elevated heavy metal concentrations, we noted a 38% increase in microbial biomass carbon (Cmic), a 15% rise in basal respiration, and a 25% decline in qCO2, which indicates an improvement in the ecological state of the soil. Evaluation of the functional diversity of microbial communities by substrate use spectra demonstrated a positive effect of biochar on the functional diversity and stability of the microbiome, with an increase of 36% in soil S1 and 54% in S2. Principal component analysis of the data set showed that the efficacy of biochar was primarily determined by the level of heavy metal pollution (R2 = 0.75).

Assessing the Efficacy of Biochar in Remediation of Polymetallic Highly Contaminated Soils with Different Levels of Humus Content

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2025年9月9日

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V. A. Terekhova,
S. A. Kulachkova,
M. V. Gorlenko

摘要

Abstract

Biochar as a soil remediation product does not always produce a promising result. In a number of studies, this is explained by the nature and properties of biochar. The dependence of the efficacy of biochar application on the level of chemical pollution and soil properties has not been sufficiently studied. The study aimed to evaluate the effects of biochar in case of heavy polymetallic contamination of agricultural sandy podzolic soils (Albic Glossic Retisols (Loamic, Aric Cutanic, Ochric) with different levels of humus content using the ecotoxicological and microbiological parameters. Soils with different organic carbon contents (S1 with C_org 3.86 and S2 with 1.30%) were sampled at two sites (Moscow oblast). It has been experimentally proven that the efficiency of biochar application depends on both the humus status of the soil and the level of chemical pollution. The soils were intentionally contaminated with elevated levels of copper (Cu), zinc (Zn), and lead (Pb) at concentrations five and ten times higher than the Approximate Allowable Concentrations (AAC) for each metal (AAC—Cu: 132 mg/kg, Zn: 130 mg/kg, Pb: 220 mg/kg according to the standard accepted in Russia). The application of biochar effectively mitigated the ecotoxicity induced by the heavy metals in the low humus soil—C_org 1.30% (S2) at the 5 AAC concentration. Specifically, we observed a 25% increase in plant root length, and a 54% rise in root biomass. However, at 10 AAC the heavy metals completely inhibited these test responses. Interestingly, in the highly humified soil—C_org 3.86%, (S1), application biochar did not result in significant improvements in the ecotoxicological and microbiological parameters, regardless of the contamination dose. A significant positive impact of biochar on the functional activity of the soil microorganisms was observed exclusively in soil S2. Under elevated heavy metal concentrations, we noted a 38% increase in microbial biomass carbon (C_mic), a 15% rise in basal respiration, and a 25% decline in qCO₂, which indicates an improvement in the ecological state of the soil. Evaluation of the functional diversity of microbial communities by substrate use spectra demonstrated a positive effect of biochar on the functional diversity and stability of the microbiome, with an increase of 36% in soil S1 and 54% in S2. Principal component analysis of the data set showed that the efficacy of biochar was primarily determined by the level of heavy metal pollution (R² = 0.75).