Interception Of Nitrogen And Phosphorus In Farmland Drainage By Ditch Pond Wetland

As an important part of the ecological environment of agricultural production, the ditch pond is a key place to intercept and transform agricultural non-point source pollution. It has multiple effects of saving water resources and purifying farmland drainage. It has a very important significance to control agricultural non-point source pollution. The main research contents of this paper are to construct the demonstration project of bioecological sewage interception and to monitor the effect of nitrogen and phosphorus removal in ditch pond wetland. I monitored the water quality of farmland drainage during rainfall period, analyzing the characteristics of nitrogen and phosphorus output. I studied the growth characteristics of dominant plants in the wetland, analyzing the removal effect of nitrogen and phosphorus by aquatic plants. I monitored the pollutant contents of nitrogen and phosphorus in water before and after the operation of the demonstration project of the ditch pond wetland, analyzing the removal effect of nitrogen and phosphorus. The results are as follows:?1?Before the rain, the concentrations of TP,TN and NH₄⁺-N are 0.35mg/L, 5.82mg/L and 1.98mg/L respectively in the demonstration area farmland drainage ditch water. At the beginning of the rainfall, the runoff of TP is up to 0.49mg/L, the runoff of TN is up to 9.73,the runoff of NH₄⁺-N is up to 3.03mg/L. The output of nitrogen and phosphorus in farmland drainage increases at first and then decreases under the condition of rainfall. After the rain stops a certain period of time, the contents of nitrogen and phosphorus pick up again. There is a significant positive correlation?P<0.01? between the pollutant discharge loads of nitrogen and phosphorus in farmland drainage and the rainfall runoff.?2?During the period of plant growth, the absorption of nitrogen and phosphorus in the root, stem and leaf of reeds and zizania caduciflora are all greater than 12mg/g. There is a linear relationship between the accumulation of nitrogen and phosphorus and the biomass of the plant. By harvesting the above ground part of reeds and zizania caduciflora, it can removal about 1130 kg nitrogen and 145 kg phosphorus from the water Per hectare per year. As a kind of floating plant cultivation, cress has obvious advantages. Not only its removal efficiency of nitrogen and phosphorus in water is good, but also the management is convenient and it can be harvested for many times. At the same time, it also has a good landscape effect.?3?For the whole year, the average removal rate of nitrogen was 34.7% and the average removal rate of phosphorus was 41.0% by the demonstration project. In July, the removal rate of nitrogen was up to 49.3%. In October, the removal rate of phosphorus was up to 52.5%.It can be concluded that, to a certain extent, seasonal changes affect the removal rate of nitrogen and phosphorus. In summer and autumn, the temperature and climate are suitable, the effect of nitrogen and phosphorus removal is the best. On the contrary, the effect of nitrogen and phosphorus removal was poor in the cold season.