Microbial responses towards biochar application in potentially toxic element (PTE) contaminated soil: a critical review on effects and potential mechanisms

Soil harbors a huge diversity of microorganisms and serves as the ecological and social foundation of human civilization. Hence, soil health management is of utmost and consistent importance, aligning with the United Nations Sustainable Development Goals. One of the most hazardous contaminants in soil matrix is potentially toxic elements (PTEs), which can cause stress in soil indigenous microorganisms and severely jeopardize soil health. Biochar technology has emerged as a promising means to alleviate PTE toxicity and benefit soil health management. Current literature has broadly integrated knowledge about the potential consequences of biochar-amended soil but has focused more on the physical and chemical responses of the soil system than microbiological attributes. In consideration of the indispensable roles of soil microbials, this paper first introduces PTE-induced stresses on soil microbials and then proposes the mechanisms of biochar's effects on soil microbials. Finally, microbial responses including variations in abundance, interspecific relationships, community composition and biological functions in biochar-amended soil are critically reviewed. This review thus aims to provide a comprehensive scientific view on the effect of biochar on soil microbiological health and its management. Sketched a mechanistic overview of PTE-induced stress towards soil microorganisms.Demonstrated a synopsis of biochar impacts on soil microbiota from both direct and indirect pathways.Discussed the development prospects of biochar technology aiming for a healthier agro-ecosystem.