Nitrogen and phosphorus removal and physiological response in aquatic plants under aeration conditions

To analyze the variation of physiological responses between Nymphaea tetragona Georgi. and Pontederia cordata L. and the water qualities under aeration conditions, the selected plants were cultivated in 12 purifying-tanks (aeration, non aeration), to treat heavily polluted river water. The characteristics of both plants were investigated, which included contents of chlorophyll and soluble protein, activities of peroxidase and catalase, accumulations of nitrogen and phosphorus, densities of tillers and roots, lengths of roots, culms and leaves, biomass of roots and shoots. The water qualities were analyzed correspondingly. Results indicated that aeration affected morphological and physiological characteristics of the plants and the water qualities and effects became more significant on N. tetragona than P. cordata. Biomass and length of roots, culms and leaves under the non aeration conditions exceeded that under the aeration conditions. Aeration contributed to the activities increase of peroxidase and catalase of the roots and the contents decrease of chlorophyll and soluble protein of the leaves. Nitrogen and phosphorus contents of the roots, culms and leaves increased under the non aeration conditions. Aeration resulted in tillers and roots densities of N. tetragona decreased, while they increased for P. cordata. Total phosphorus and soluble phosphorus removals decreased 8.42% and 8.05% in the tank with N. tetragona under the aeration conditions. In the tank with P. cordata, total nitrogen and NH₄₊ -N removals increased 14.44% and 16.06% under the aeration conditions. This work provided valuable data for optimizing the plants allocation in the ecological restoration project of the polluted water.