Nitrogen And Phosphorus Retention And Purification In Pond Wetland System

In recent years there is a lot of the research that studies on controlling pollution source and treating polluted lake, and it is little that studies on the pollutant of intercepting, transporting and transforming for the hollow structure of the conjunction of the farmland—lake system(such as pond, ditch). The hollow belt not only can adsorb and intercept non-point source pollutant, but also can purify water quality. The main aim of this thesis is to research the transporting regulation and the retention effect of N and P for the different dimensions pond wetland system.The main methods of this thesis include the field inquisition, observation on the spot, chemical analysis and the theories analysis and research. The main contents include: (1)Investigate the biology community of the pond wetland system in the certain scope, and analyse variety regulation of the pond wetland system in the different period;(2)Compute the gross of N and P entering the pond with the rainfall under the different peripheric plants in the different period, and the quantity of N and P retented in the unit area;(3)Compute the gross of N and P retented by the pond wetland system with the rainfall in the different period , and analyse variety regulation of N and P in the pond wetland system;(4)Analyse the relation between TN, NH₄⁺- N, NO₃^-—N and NO₂^--N in the pond wetland system.The results show that:(1) the different dimensions pond wetland system's retention effect of N and P relates to not only itself cubage and the ability of purification of itself, but also its characteristic of the place and its catchments area; (2) In the period of little rainfall, because the water level in pond is lower, the most of N and P is intercepted after input to pond wetland with rain runoff, and only little run off pond entering the rivers and lakes. The abundant rainfall period (at April-July generally) is time to apply fertilizer, so the quantity of N and P is much that input to pond wetland with rain runoff. Although the water level of the pond is higher and the retention ability for the rain runoff drop, the purifying ability of the pond-wetland system is very strong. Its main performance is cutting down the density of the nourishment (such as N and P etc.) in the short time, and improve the water quality; (3) In the pond wetland system the purifying effect of the N and P is closely related to season, hydrophytes, depth of water and the overlay degree of hydrophytes facts etc.