Impact of nanoplastics on the biodegradation, ecotoxicity, and key genes involved in imidacloprid metabolic pathways in papyrus (Cyperus papyrus L.)

Both nanoplastics (NPs) and imidacloprid (IMI) are widely distributed in the environment and have attracted significant attention due to their adverse effects on ecosystems. Constructed wetlands have the potential to remove IMI, but there is still limited understanding of how wetland plants interact with IMI, especially when influenced by different charged NPs. This study assessed their ecotoxicological effects, as well as the fate and transformation of IMI in papyrus (Cyperus papyrus L.) under the influence of different charged NPs and identified key driving genes in the plant. Results show that simultaneous exposure to positively charged PS-NH2 and IMI inhibited plant growth. The combined action of NPs and IMI intensified their toxicity, enhancing lipid peroxidation and altering antioxidant enzyme activities. The IMI removal efficiency, which was primarily driven by biodegradation, was 80.61%, 88.91%, and 74.71% in the IMI-alone, co-IMI/PS_COOH, and co-IMI/PS_NH2 systems, respectively. PS-NH2 restricted the roots-to-shoots translocation ability of IMI. PS-COOH enhanced IMI oxidation and nitro reduction, while PS-NH2 inhibited 2-OH-IMI dehydrogenation to IMI-olefin in papyrus. Transcriptomics and gene network analysis identified the genes encoding CYP450 enzymes, reductases, hydrolases, dehydrogenases, and peroxidases as those influencing IMI biodegradation. These enzymes play a crucial role in the hydroxylation, dehydrogenation, reduction, and oxidation processes during biodegradation of IMI in the presence of NPs. This study expands the understanding of the impact of differently charged NPs on the IMI remediation efficacy of papyrus, thus providing new insights into the phytoremediation of organic contaminants in constructed wetlands.