In recent environmental research, innovative methods for remediating cadmium (Cd)-contaminated soil have shown promise in mitigating its harmful effects on earthworms, indicating a significant step forward in ecological restoration practices. The study focused on the use of biochar-supported nanoscale zero-valent iron (nZVI@BC) and its green synthesis counterpart, GnZVI@BC, which is reduced by green tea extract. These substances were investigated for their potential to immobilize Cd in the soil, thus preventing its uptake by earthworms (Eisenia foetida), a species known for its sensitivity to soil contaminants.

The findings revealed that both nZVI@BC and GnZVI@BC were effective in reducing oxidative stress, lipid peroxidation, and DNA damage in earthworms exposed to Cd. Additionally, the gene toxicity exerted by Cd was restrained, with a stabilization in the expression of sod (superoxide dismutase), cat (catalase), and gst (glutathione S-transferase) genes, which are crucial for the earthworm’s defense against oxidative stress. The study further explored the main pathways affected by differential gene expressions, including cellular oxidative phosphorylation and transforming growth factor-β signaling pathways with nZVI@BC, and cell phagosome structure, as well as the metabolism of taurine, hypotaurine, and alanine processes with GnZVI@BC.

This research is not only pivotal for understanding the ecological impacts of nZVI@BC on soil fauna but also offers valuable insights for the ecological risk assessment of such remediation technologies. By demonstrating the reduced harmful effects of Cd on earthworms through the application of nZVI@BC and GnZVI@BC, the study underscores the potential of these materials in enhancing soil health and supporting the ecosystem’s natural recuperation processes.