Synergistic effects of microplastics and sulfonamide on greenhouse gas emissions in agricultural ditch sediments: Insights into microbial interactions.

Recently, concerns have been raised regarding concurrent pollution by microplastics and antibiotics in agricultural aquatic ecosystems. However, knowledge gaps remain regarding their combined effects on greenhouse gas (GHG) emissions and bacterial community assembly mechanisms. To address this, a microcosm experiment was performed to investigate the GHG (CH4, CO2, and N2O) emission characteristics and bacterial community assembly mechanisms in agricultural ditch sediments under co-exposure to different microplastics (polythene (PE), polylactic acid (PLA)), and sulfanilamide (SA). The global warming potential (GWP) of the different treatments was ranked as follows: SA+PLA (162.96 mg/m2/h) > PLA (123.49 mg/m2/h) > SA (121.75 mg/m2/h) > SA+PE (102.33 mg/m2/h) > CK (without microplastics or antibiotics, 84.67 mg/m2/h) > PE (78.29 mg/m2/h). Additionally, a phylogenetic bin-based null model and molecular ecological network analysis indicated that SA-induced selective pressures reduced compositional turnover, whereas microplastics enhanced drift effects and decreased network robustness. The co-contamination of SA with different microplastics exhibited the opposite effect on the network and assembly process, suggesting that disturbance-mediated species dominance alters the colonization of rare species. Collectively, these findings provide valuable evidence that the synergistic effects of biodegradable microplastic and SA can promote GHG emissions and influence the mechanisms underlying community assembly processes.