Enhancing nitrogen management in aerated landfills: Quantifying fungal contributions to nitrification using a model-based approach.

Effective nitrogen management is critical for minimizing environmental risks in municipal solid waste (MSW) landfills. In-situ aeration has emerged as a practical strategy to accelerate waste stabilization and improve nitrogen stabilization. However, the role of fungi in regulating nitrogen transformation processes-particularly nitrification-remains insufficiently understood. This study investigates fungal contributions to microbial nitrification in 16 simulated aerated landfill systems under varying aeration and substrate conditions. Selective microbial inhibition enabled the construction of fungal-dominated systems. Leachate NOx (nitrite + nitrate) accumulation exhibited a triphasic pattern, within which the S-shaped nitrification phase was well described by a modified Logistic model under favourable conditions. Model parameter M (the maximum accumulated concentration of nitrification products) enabled robust quantification of fungal contributions ranging from 6.46 % to 94.94 % of total microbial nitrification while the maximum contribution occurred under ammonia-deficient conditions. Structural equation model further identified ammonia concentration and temperature as primary drivers of total nitrification, whereas fungal nitrification was most influenced by ammonia and oxygen levels. Crucially, oxygen content and temperature governed the extent of fungal contribution to total nitrification. Notably, Aspergillus fumigatus emerged as a key fungal species driving fungal nitrification and its contribution. These findings highlight fungi as key microbial players in landfill nitrogen cycling, offering new insights for optimizing nitrogen management through aeration strategies in landfill operations.