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Purpose <p>Low molecular organic acids (LA) are key components of plant root exudates and critically influence the efficiency of biochar (BC) in remediating cadmium-contaminated soils. Therefore, exploring how LA types and addition sequences affect BC’s performance can help determine the optimal timing for BC utilization in soil cadmium (Cd) immobilization.</p> Methods <p>In this study, BC and different LAs were applied to soil in specific sequences to simulate three agricultural phases: biochar-first sequence (before crop establishment), simultaneous addition sequence (during the sowing phase), and LA-first sequence (after crop emergence). This design aimed to identify the optimal addition timing for BC to enhance cadmium removal within the crop root zone.</p> Results <p>Our study revealed that BC was the primary factor responsible for Cd adsorption, and LA modification significantly enhanced the Cd adsorption capacity of BC. When LA was applied after biochar amendment, it increased soil pH and organic matter content and reduced Cd bioavailability. Specifically, tartaric acid increased the activities of sucrase, urease, and catalase by 59.5% to 159.1%, elevated total soil enzyme activity (TEA) by 0.64 units, and decreased the content of exchangeable Cd (EXE-Cd) by 8.15%. In contrast, malic acid increased available phosphorus (AP) and potassium (AK) by 90.24% and 60.87%, respectively. Structural equation modeling further demonstrated that specific LA treatments (particularly tartaric acid) and the biochar-first strategy significantly facilitated the reduction of Cd bioavailability, with chemical characteristics of specific LAs playing a dominant role in EXE-Cd removal.</p> Conclusion <p>The selection among tartaric, citric, and malic acid treatments, as well as the comparison among biochar-first, simultaneous, and LA-first addition strategies, significantly influenced the Cd immobilization efficiency of biochar in soil. Specifically, applying LA after BC amendment (a common practice before crop establishment) resulted in the lowest content of EXE-Cd, and tartaric acid induced the greatest reduction in EXE-Cd among the tested LA.</p>

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Types and addition sequences of low molecular organic acids impact the remediation efficiency of cadmium-contaminated soil by biochar

  • 期刊论文

  • 发表日期：

    2026年2月17日

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  • Yunfeng Gao,
  • Yang Jiang,
  • Meiqi Chu,
  • Xu Zhang,
  • Yue Jiang,
  • Jiaqi Zhang,
  • Wei Wang,
  • Xuesheng Liu,
  • Sha Li,
  • Juanjuan Qu,
  • Hongyu Ren

摘要

Purpose

Low molecular organic acids (LA) are key components of plant root exudates and critically influence the efficiency of biochar (BC) in remediating cadmium-contaminated soils. Therefore, exploring how LA types and addition sequences affect BC’s performance can help determine the optimal timing for BC utilization in soil cadmium (Cd) immobilization.

Methods

In this study, BC and different LAs were applied to soil in specific sequences to simulate three agricultural phases: biochar-first sequence (before crop establishment), simultaneous addition sequence (during the sowing phase), and LA-first sequence (after crop emergence). This design aimed to identify the optimal addition timing for BC to enhance cadmium removal within the crop root zone.

Results

Our study revealed that BC was the primary factor responsible for Cd adsorption, and LA modification significantly enhanced the Cd adsorption capacity of BC. When LA was applied after biochar amendment, it increased soil pH and organic matter content and reduced Cd bioavailability. Specifically, tartaric acid increased the activities of sucrase, urease, and catalase by 59.5% to 159.1%, elevated total soil enzyme activity (TEA) by 0.64 units, and decreased the content of exchangeable Cd (EXE-Cd) by 8.15%. In contrast, malic acid increased available phosphorus (AP) and potassium (AK) by 90.24% and 60.87%, respectively. Structural equation modeling further demonstrated that specific LA treatments (particularly tartaric acid) and the biochar-first strategy significantly facilitated the reduction of Cd bioavailability, with chemical characteristics of specific LAs playing a dominant role in EXE-Cd removal.

Conclusion

The selection among tartaric, citric, and malic acid treatments, as well as the comparison among biochar-first, simultaneous, and LA-first addition strategies, significantly influenced the Cd immobilization efficiency of biochar in soil. Specifically, applying LA after BC amendment (a common practice before crop establishment) resulted in the lowest content of EXE-Cd, and tartaric acid induced the greatest reduction in EXE-Cd among the tested LA.