A new study has revealed a promising nature-based strategy to clean up red mud, one of the world's most hazardous industrial wastes, by combining biochar with beneficial soil fungi to target specific pollutants and revive damaged soils.
"By matching the right fungal species with specific metal contaminants, we can dramatically improve both detoxification efficiency and soil recovery," said the study's corresponding author. "This opens the door to more precise and scalable remediation strategies for contaminated land."
Red mud is a highly alkaline waste produced during aluminum manufacturing. It contains toxic metals such as arsenic and lead and poses serious environmental risks when stored in large quantities. Its extreme chemical conditions also make it difficult for plants to survive, limiting the effectiveness of traditional remediation approaches.
In this study, researchers developed a new system that combines biochar, a carbon-rich material made from biomass, with arbuscular mycorrhizal fungi, which form symbiotic relationships with plant roots. They tested two fungal species, Funneliformis mosseae and Rhizophagus intraradices, in combination with biochar and a resilient plant species, Arundo donax, also known as giant reed.
The results showed that each fungal species played a distinct role. Biochar combined with Funneliformis mosseae enhanced plant photosynthesis and antioxidant defenses while significantly reducing the mobility of arsenic in the soil. This helped plants better tolerate the harsh conditions and reduced the ecological risk of arsenic contamination.
In contrast, biochar combined with Rhizophagus intraradices promoted plant growth and biomass production while effectively immobilizing lead and reducing soil salinity. It also increased microbial diversity and activated key soil enzymes involved in nutrient cycling, particularly phosphorus.
The researchers describe this approach as a "fungal species–metal valency matching" strategy. In simple terms, different fungi are better suited to handle different types of metals based on their chemical properties. Arsenic, which exists as negatively charged ions, was more effectively stabilized by Funneliformis mosseae, while positively charged lead was better targeted by Rhizophagus intraradices.
Beyond metal detoxification, the combined treatments also improved overall soil health. The system reduced soil alkalinity, lowered salt content, and enhanced nutrient availability. For example, one treatment significantly increased soil organic carbon and nitrogen, while another improved phosphorus availability and microbial diversity.
Advanced microbial analyses revealed that specific bacterial groups played key roles in these processes. Some microbes contributed to carbon accumulation, while others enhanced enzyme activity linked to nutrient cycling. These findings highlight the importance of plant–microbe interactions in restoring degraded soils.
Importantly, the study suggests a practical pathway for real-world application. In areas where arsenic contamination is dominant, biochar combined with Funneliformis mosseae may be most effective. In regions with high levels of lead and salinity, biochar combined with Rhizophagus intraradices could provide better results.
This targeted approach represents a shift from one-size-fits-all remediation strategies to more precise, science-based solutions tailored to specific contamination profiles.
As industrial waste continues to accumulate globally, innovative and sustainable solutions like this could play a crucial role in turning polluted land into productive ecosystems once again.
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Journal Reference: Wang, X., Sun, Y., Zeng, D. et al. Biochar-loaded AM fungi coupled with Arundo donax enable targeted red mud remediation via valency—specific metal detoxification and soil function recovery. Biochar 8, 52 (2026).
https://doi.org/10.1007/s42773-025-00568-7
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.
