Compound-specific effects of phthalate esters on nitrogen cycling and N₂O emissions in paddy soils under contrasting...

Phthalates (PAEs) are commonly used as plasticizers and agrochemical additives, easily released and accumulated in soils. As emerging organic pollutants, how PAEs affect soil nitrogen (N) cycling remains unclear. Here, a 91-day microcosm experiment was conducted to investigate the response of functional microorganisms and nitrous oxide (N₂O) emissions to dimethyl phthalate (DMP) and di(2-ethylhexyl) phthalate (DEHP) enrichment under different moisture regimes. Metagenomic analysis showed that PAE type, rather than concentration, predominantly shaped microbial community structure and N-cycling functional profiles. Under unflooded conditions, DEHP increased cumulative N₂O emissions by 42%, accompanied by enhanced nitrification potential, higher abundances of amoA and hao, and enrichment of Nitrosospira. Conversely, DMP and co-exposure treatments reduced cumulative N₂O emissions by 49.24-67.86%, together with suppressed autotrophic nitrification and increased denitrification module abundance. Under flooded conditions, DMP and co-exposure increased nosZ abundance and enriched Telmatospirillum, indicating a greater potential for N₂O reduction. In addition, PAE exposure increased the complexity of microbial co-occurrence networks and strengthened associations between functional taxa and N-cycling genes. Structural equation modelling showed that PAE-induced shifts in soil pH, dissolved organic carbon, and inorganic N pools jointly regulated nitrification and denitrification pathways, thereby determining N₂O emission patterns. These findings highlight the potential for plasticizer contamination to reshape nitrogen transformation and nitrogen loss pathways in paddy soils under contrasting moisture regimes.