Biochar mitigates the biotoxicity of heavy metals in livestock manure during composting

Abstract

The addition of biochar could mitigate the bioavailability of heavy metals during livestock manure composting. However, the main action mechanism of biochar, such as how it worked, was ambiguous. Therefore, in this study, materials (biochar, alkali modified biochar, pretreated cotton ball) were added by embedding with nylon mesh bags to explore the adsorption performance of added materials and its influence on the composting process. The results showed that embedded materials promoted the formation of humic acid and reduced the distribution proportion of bioavailable fraction of heavy metals during composting (Cu: at least 15.72%; Zn: at least 33.44%). The surface of biochar extracted from composting contained attachments, however, the attachment of heavy metal was not detected and functional groups on the materials did no change significantly. This indicated that the addition of biochar did not directly adsorb heavy metals. Most notably, the microbial network changed after embedding materials, and the succession of microbial community promoted the formation of humic acid. Ultimately, structural equation models verified that embedded materials promoted the formation of humic acid through stable microbial groups, thereby accelerating the passivation of heavy metals during composting. This study provides theoretical and technical supports for mitigating the biotoxicity of heavy metals by biochar during composting. Graphical Abstract

Unveiling the Role of Dissolved Organic Matter on the Hg Phytoavailability in Biochar-Amended Soils

“…The biochar was packed into acid-washed microporous mesh nylon bags (pore size 0.05 mm). This was aimed at preventing biochar particles from leaching into the soil, as well as allowing the transport of Hg [ 37 , 38 ]. The bagged biochar and 12 g of soil were placed sequentially in a 50 mL polypropylene centrifuge tube so that the biochar could be uniformly and tightly encapsulated by the soil.…”

Combined Application Effects of Arbuscular Mycorrhizal Fungi and Biochar on the Rhizosphere Fungal Community of Allium fistulosum L.

“…LEfSe analysis can indicate both statistical significance and biological relevance. Gephi software was used to visualize the symbiotic network [ 26 ]. Zi-Pi diagrams of the connection values of all modules in the fungal ecological network are generated to explore the potential topological role of specific nodes in the network, while nodes are classified according to their Zi-Pi coefficients, and the topological role of each node is determined.…”