Roles of adding biochar and montmorillonite alone on reducing the bioavailability of heavy metals during chicken manure composting

The aim of this study was to explore the effects of adding biochar and montmorillonite alone on the correlations between bacteria and bioavailability of heavy metals (HM) during chicken manure composting. Three composting experiments were conducted, containing the without ameliorant, 10% biochar and 10% montmorillonite. The results showed that biochar and montmorillonite ameliorants significantly reduced the bioavailability of Cu by 90.3%, 81.2%, while that of Zn by 11.7%, 15.6%, respectively. Meanwhile, they also significantly changed bacterial community structure and enhanced the correlation between bacterial bands (i.e., 19, 24, 26 and 30) and HM fractions. This correlation was validated in network analysis. Structural equation models further confirmed that bacteria had a complete and effective pathway to influence the bioavailability of HM. In summary, this study suggested that biochar and montmorillonite additions were an effective regulation method to reduce the bioavailability of HM from composting system.