Abstract
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•FeONPs (α-Fe2O3 NPs and Fe3O4 NPs) were added into the composting system.•FeONPs, especially α-Fe2O3 NPs, reduced TN loss and reserved more mineral N.•AOB decrease by FeONPs was more important than AOA in weakening NH4+-N oxidation.•Bacterial community composition at phylum level did not shift with FeONPs addition.•Final compost quality was improved with addition of FeONPs, especially α-Fe2O3 NPs.
Composting amended with iron oxide nanoparticles (FeONPs, α-Fe2O3 and Fe3O4 NPs) were conducted to study the impacts of FeONPs on nitrogen conservation and microbial community. It was found that amendment of FeONPs, especially α-Fe2O3 NPs, reduced total nitrogen (TN) loss, and reserved more NH4+-N and mineral N. Pearson correlation analysis revealed that decrease of ammonia-oxidizing bacteria (AOB) in FeONPs treatments played more important role than ammonia-oxidizing archaea (AOA) in reserving more NH4+-N and mineral N, and reducing TN loss. Bacterial community composition at phylum level did not shift with addition of FeONPs. Firmicutes, Actinobacteria, and Proteobacteria were the three most dominant phyla in all treatments. Overall, this study provides a method to reduce TN loss and improve mineral N reservation during composting, and gives a deep insight into the role of AOB and AOA in nitrogen transformation.