Effects of nanopolystyrene addition on nitrogen fertilizer fate, gaseous loss of N from the soil, and soil microbial community composition

Nanoplastics and microplastics are the degradation products of plastics waste and have become a dominant pollutant in the environment. However, little is known about the ecological impacts of nanoplastic particles in the agroecosystem. We conducted a mesocosm experiment to examine nanopolystyrene effects on fertilizer nitrogen (N) fate, N gaseous losses and soil microbial communities using Chinese cabbage (Brassica Campestris ssp.) as the model plant. The two-factorial experiment was designed as the addition of ¹⁵N-labeled urea exposed without and with ~50 nm nanopolystyrene (0, 0.05%, and 0.1%). Nanopolystyrene addition had a detectable effect on soil mineral N content. The ¹⁵N uptake of plants was reduced in aboveground biomass but enhanced in roots with increasing nanopolystyrene concentration. Nanopolystyrene addition decreased soil nitrous oxide and ammonia emissions by 27% and 37%, respectively. Nanopolystyrene addition consistently reduced the abundance of ammonia oxidizer genes but showed contrasting effects on denitrifying genes. Metagenomic sequencing data revealed no significant effects of nanopolystyrene on the N-cycle pathway, while it significantly altered the composition of bacterial and fungal communities. This study provided the first insights into the nanopolystyrene induced linkage of root growth with more root N uptake and less gaseous N losses and the associated changes in the microbial community.