Function of aquatic plants on nitrogen removal and greenhouse gas emission in enhanced denitrification constructed wetlands: Iris pseudacorus for example

Aquatic plants play an important role on denitrification and greenhouse gas emissions in wetlands, but the contribution of plants in the enhanced denitrification wetlands with extra carbon source remains poorly understood. The experimental constructed wetlands were set up to investigate the function of aquatic plants (Iris pseudacorus) on nitrogen removal and greenhouse gas emission coupled with different organics dosages. With the increase of organics addition, the total nitrogen removal rate in the wetland with plants increased to 96.89%, while only 86.60% in the unplanted wetland due to restricted nitrification. The existence of plants maintained the abundance of ammonia oxidation bacteria like Nitrosospira and Nitrosomonas and amoA gene through oxygen transport when extra carbon source addition. For greenhouse gases, wetlands with plants mainly acted as the carbon sink (about 13,000 mg m−2 d−1 net carbon dioxide absorption flux) and could cover the emission of nitrous oxide and methane (maximum 12.24 mg m−2 d−1 and 2.52 mg m−2 d−1 respectively). It could be concluded that aquatic plants benefitted nitrification-denitrification process and the control of greenhouse gases release in the enhanced denitrification wetlands.