Effects of macrophytes on micro-And nanoplastic retention and cycling in constructed wetlands

Macrophytes play the important roles in purifying pollutants of constructed wetlands (CWs), while their effects on CWs exposed to micro/nano plastics are not clear. Therefore, planted and unplanted CWs were established to reveal the impacts of macrophytes (Iris pseudacorus) on the overall performance of CWs under polystyrene micro/ nano plastics (PS MPs/NPs) exposure. Results showed that macrophytes effectively enhanced the interception capacities of CWs to PS NPs, and significantly promoted the removal of nitrogen and phosphorus after exposed to PS MPs/NPs. Meanwhile, macrophytes improved the activities of dehydrogenase, urease, and phosphatase. Sequencing analysis showed that macrophytes optimized the composition of microbial communities in CWs and stimulated the growth of functional bacteria involved in nitrogen and phosphorus transformation. Moreover, macrophytes further altered the absolute abundance of nitrogen transformation functional genes (amoA, nxrA, narG and nirS). Functional annotation analysis revealed that macrophytes promoted metabolic functions such as Xenobiotics, Amino acids, Lipids metabolism and Signal transduction, ensuring the metabolic balance and ho-meostasis of microbes under PS MPs/NPs stress. These results exhibited profound implications for the compre-hensive evaluation on the roles of macrophytes in CWs for treating wastewater containing PS MPs/NPs.

Automated summary

Macrophytes enhance the efficiency of constructed wetlands in removing polystyrene micro/nano plastics (PS MPs/NPs) through increased interception and improved microbial activity. They also optimize the composition of microbial communities and stimulate the growth of functional bacteria involved in nitrogen and phosphorus transformation. Furthermore, macrophytes promote metabolic functions and maintain microbial homeostasis under PS MPs/NPs stress, ensuring the efficiency of wetlands in treating wastewater containing PS MPs/NPs.