Comparing kitchen-waste biochars revealed that high-temperature biochar creates stable conditions that enhance microbial-assisted cadmium (Cd) immobilization and limit crop uptake. In contrast, low-temperature biochar improves soil fertility but can stimulate microbial activity that increases cadmium availability.
Heavy metal contamination is an increasing global agricultural challenge driven by industrialization and long-term agrochemical use. Cd is especially concerning due to its high mobility, accumulation in crops, and risks to food safety and human health. Approximately 14–17% of global farmland is affected by toxic metals, emphasizing the need for sustainable remediation strategies. Biochar, a carbon-rich material derived from biomass, has attracted attention for its porous structure, stability, and metal-binding capacity. However, biochars produced at different temperatures exhibit distinct physicochemical properties, resulting in variable remediation performance. Growing evidence shows that soil microbes actively regulate metal behavior, yet how biochar properties shape microbial responses and cadmium stabilization remains unclear.
A study (DOI: 10.48130/ebp-0025-0019) published in Environmental and Biogeochemical Processes on 15 January 2026 by Quan Chen’s team, Kunming University of Science & Technology, reveals that successful heavy-metal remediation depends not only on material properties but also on carefully managing biochar–microbe interactions.
Using a controlled pot experiment, researchers amended cadmium-contaminated soil planted with Brassica chinensis using kitchen-waste biochar produced at 300, 500, and 700 °C, applied either alone or combined with Escherichia coli to simulate microbial intervention. They quantified rhizosphere total Cd, BCR sequential fractions (F1–F4), and plant uptake and translocation, while simultaneously characterizing soil and biochar physicochemical properties—including dissolved organic carbon (DOC), surface area, electrical conductivity (EC), FTIR functional groups, and enzyme activities—and profiling microbial communities through high-throughput sequencing and co-occurrence network analysis. After 70 days, rhizosphere total Cd decreased by 29.77–41.22% relative to the initial 1.31 mg kg⁻¹, indicating both natural migration and biochar-mediated adsorption that limited Cd leaching. Pyrolysis temperature strongly controlled Cd mobility: acid-extractable Cd (F1) declined by 4.22%, 13.44%, and 28.34% under KB300, KB500, and KB700, respectively, while bioavailable Cd (F1+F2) fell by 2.25%, 8.78%, and 22.25%, demonstrating that stabilization primarily resulted from suppressing the most mobile fraction. Plant responses mirrored these patterns. Low-temperature biochar reduced root Cd but increased leaf accumulation and root-to-leaf transport, suggesting enhanced mobilization driven by microbial activity and organic acid release. In contrast, 700 °C biochar promoted Cd retention in roots and reduced accumulation in aerial tissues, thereby lowering food-safety risks. Mechanistically, increasing pyrolysis temperature sharply reduced DOC (12.37 → 0.03 mg kg⁻¹) while expanding surface area (0.14 → 16.81 m² g⁻¹) and increasing soil EC by up to 142%, creating mineral-rich environments favorable for Cd precipitation and complexation. Microbial analyses revealed that high-temperature biochar decreased overall bacterial diversity but selectively enriched Cd-stabilizing taxa such as Bacillus, Rhodococcus, and Mucor, forming simpler yet more tightly connected ecological networks. Microbial inoculation further highlighted temperature-dependent biochar–microbe interactions: E. coli alone had minimal effects, but when combined with low-temperature biochar it increased Cd bioavailability and plant uptake, whereas coupling with high-temperature biochar reinforced immobilization and minimized Cd translocation to shoots. Together, the findings demonstrate that Cd stabilization arises from a temperature-governed synergy between biochar physicochemical properties and microbial community restructuring.
This study reveals that biochar acts as both a physicochemical stabilizer and a microbial regulator in cadmium-contaminated soils. Temperature-tailored biochar application, particularly high-temperature biochar derived from organic waste, enhances Cd immobilization, reduces crop contamination risks, and promotes soil health. Such selective strategies offer a sustainable pathway for safe farmland remediation and circular biomass utilization worldwide.
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References
DOI
10.48130/ebp-0025-0019
Original Source URL
https://doi.org/10.48130/ebp-0025-0019
Funding Information
This research was supported by the National Key Research and Development Program of China (2023YFC3709100), and the National Natural Science Foundation of China (42130711, 42477245, 42377250, and 42407346).
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