Iris pseudacorus as precursor affecting ecological transformation of graphene oxide and performance of constructed wetland

The role of plants is largely unknown in constructed wetlands (CWs) exposed to phytotoxic nanomaterials. Present study investigated transformation of graphene oxide (GO) and performance of CWs with Iris pseudacorus as precursor. GO was trapped by CWs without dependence on plants. GO could move to lower substrate layer and present increases on defects/disorders with stronger effects in planted CW. Before adding GO, planted CW achieved better removal both of phosphorus and nitrogen. After adding GO, phosphorus removal in planted CW was 93.23-95.71% higher than 82.55-90.07% in unplanted CW. However, total nitrogen removal was not improved, showing 48.20-56.66% and 53.44-56.04% in planted and unplanted CWs. Plant improved urease, phosphatase, and arylsulfatase, but it decreased beta-glucosidase and had less effects on dehydrogenase and catalase. Pearson correlation matrix revealed that plant enhanced microbial interaction with high degree of positive correlation. Moreover, there were obvious shifts in microbial community at phylum and genus level, which presented closely positive action on substrate enzyme activities. The functional profile was less affected due to functional redundancy in microbial system, but time effects were obvious in CWs, especially in planted CW. These findings could provide the basis on understanding role of plants in CWs for treating nanoparticles wastewater.

Automated summary

The role of plants in constructed wetlands exposed to phytotoxic nanomaterials is largely unknown. This study investigated the transformation of graphene oxide (GO) and the performance of wetlands with Iris pseudacorus as a precursor. The results showed that GO could be trapped by the wetlands independent of plants and that GO movement to lower substrate layer resulted in increases in defects/disorders, particularly in planted wetlands. Before adding GO, the planted wetland achieved better removal of both phosphorus and nitrogen. After adding GO, phosphorus removal was significantly higher in the planted wetland compared to the unplanted wetland, while nitrogen removal was not improved. The activities of certain substrate enzymes were improved by plants, and there were significant shifts in the microbial community in response to the presence of plants.