Study On The Fate Of Nonpoint Source Pollutants-Nitrogen And Phosphorus In The Protection Forest System

Various paths of vegetation assimilation, retention of soil adsorption and microbial degradation on removing nitrogen and phosphorus in different seasons were investigated in a small scale typical protection forest around the Chaobai River basin in order to solve the problem of these nonpoint source pollutants exposed into the Mi-yun Reservoir with storm runoff. The experimental results showed that the contents of nitrogen and phosphorus absorbed by various vegetations are different, and they observably increase in growth period. In the contrary, soil nitrogen and phosphorus contents in dormant period are higher than vegetation period. Microbial degradation is closely related to nitrogen and phosphorus removal. Soil in the protection forest system can adsorb and remove nitrogen and phosphorus, especially have an effect on adsorption of phosphorus. And the absorption of vegetation is one of the main approaches to remove nitrogen and phosphorus pollutants from the soil. Besides that, there are several vegetation in Beijing which have better effect on absorbing nitrogen and phosphorus are recommended for removing nonpoint source pollutants.Analyzing nitrogen and phosphorus mass balance in growing and dormant period, the removal mechanism of nitrogen and phosphorus in the protection forest system was brought forward. The removal of nitrogen and phosphorus pollutants is mainly relied on the assimilation and accumulation by evergreen arbor and deciduous woody plants'branches and roots. Herbs in the protection forest system can absorb nitrogen and phosphorus pollutants rapidly when storm runoff generated in quantity. If herbs die, they would tardily discharge nitrogen and phosphorus for growth of evergreen arbors and deciduous plants. Herbs play an important role of regulating the time, nitrogen and phosphorus released, in the system. Comparing the absorption of nitrogen and phosphorus by different kinds of plants in typical protection forest around the Chaobai River basin, the vegetation which has better effect on assimilation and absorption for nitrogen and phosphorus is selected and combined. That provides a reference to select vegetation and optimize space allocation of protection forest system on the purpose of controlling nitrogen and phosphorus pollutants. Achieve the goal of removing nonpoint source pollutants-nitrogen and phosphorus ultimately.