Effect of iron plaque on the root surface of hydrophyte on nitrogen and phosphorus transformation

Plants play an important role in constructed wetlands. However, the effect and mechanism in nutrient removal of iron plaque on the root surface were explained unclear. Because of the complexity of wetland system, this paper used hydroponics system to proceed the research. In this study, cattails were firstly cultured at 10% Hoagland's nutrient solution with 20 mg/L Fe2+ (Fe2+ as FeSO4·7H2O) for iron plaque formation, and then transplanted to growth chamber to examine the promoting effect and mechanism of pollutant removal. Compared with control groups without iron plaque, the average removal efficiency of COD, NH4+-N, NO3−-N and the total phosphorus (TP) improved significantly (P = 0.000 < 0.05). Iron plaque could enhance the related microbial processes and aerobic environment underwater, thus further facilitated pollutant removal. The results indicate that iron plaque on the root surface could enhance the removal performance of nitrogen and phosphorus in the aquatic environment.