Ghandali, et al (2024) Heavy metals immobilization and bioavailability in multi-metal contaminated soil under ryegrass cultivation as affected by ZnO and MnO₂ nanoparticle-modified biochar. Scientific Reports. https://doi.org/10.1038/s41598-024-61270-5

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Pollution by heavy metals (HMs) presents a significant challenge for agriculture and environmental health globally. Traditional soil remediation techniques are often costly and can damage soil structures. This study explores the potential of pristine biochar and biochar modified with manganese dioxide (BC@MnO2) and zinc oxide (BC@ZnO) nanoparticles to immobilize and reduce the bioavailability of lead (Pb), cadmium (Cd), zinc (Zn), and nickel (Ni) in contaminated soils.

Using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), Fourier-transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD), the successful incorporation of ZnO and MnO2 nanoparticles into biochar was confirmed. The research revealed that both modified and pristine biochar significantly enhanced the dry weight of ryegrass (Lolium perenne L.) roots and shoots. Specifically, the BC@MnO2 treatment resulted in the highest biomass production.

More crucially, the study demonstrated that the addition of biochar, particularly BC@MnO2, significantly reduced the uptake of HMs by ryegrass. The BC@MnO2 treatment showed the lowest levels of Pb, Cd, Zn, and Ni in plant shoots. This indicates a notable reduction in the bioavailability of these metals.

Moreover, the translocation factor (TF) and bioconcentration factors were lowest in the 1% BC@MnO2 treatment, highlighting its superior effectiveness in immobilizing HMs. Ryegrass itself showed a strong capacity to accumulate HMs in its roots, making it an ideal plant for phytostabilization.

This study concludes that modified biochar, especially with MnO2 nanoparticles, is a highly efficient, cost-effective amendment for remediating HM-contaminated soils, improving plant growth while reducing HM bioavailability.