Small molecule carbon sources drivers increase in heavy metal passivation during chicken manure composting by...

The application of compost products to the soil impacts the soil microenvironment. Optimize the composting process is essential to minimize potential harm to the soil. This research aims to explore the effects of small molecular carbon source (SMCS) additives on the transformation of heavy metal (HM) fractions, bacterial community structure and metabolism functions to better comprehend the degradation of organic compounds and HM passivation during composting. The results indicate that the addition of SMCS accelerates the degradation of organic matter and total organic carbon. The exchangeable fraction (F1) of HM was effectively reduced. After adding SMCS, a significant change was observed at family and species levels in the 17th days, accounting for 20.0 %, 17.2 % and 32.3 %, 7.8 % respectively. Additionally, the incorporation of SMCS enhances the abundance of carbohydrate metabolism and amino acid metabolism pathways, while also modulating the microbial community composition essential for the effective transformation of HM fractions during the composting process. Finally, Variance partitioning analysis (VPA) results reveal that both environmental indicators and microbial communities play a role in metabolic function, with microbial community composition more significantly (explanation 22.8 %). These findings are of great significance for regulating HM passivation through metabolic pathways and achieving the green recycling of organic wastes.