Research On Ecological Dynamic Model Of Nitrogen Cycle Of Phytoremediation Of Farmland Drainage

Water pollution is one of the most important factors contributing to the global water shortage.In recent years,the pollution of farmland has resulted in the eutrophication of surface water bodies,which has attracted more and more attention.Phytoremediation is to use specific aquatic or terrestrial plants for water pollutants such as nitrogen in situ absorption,degradation and fixing,with features of low consumption and good effect,and it is gradually used in sewage disposal.But the study showed that the phytoremediation technology of removing nitrogen pollutants had good effect.The understanding of its impact factor is not comprehensive enough since people study it recently,and related dynamics research is not much.So the accuracy of many models is not enough,and the selection of reaction parameters is not unified.In this paper,free water surface flow constructed wetland,vertical subsurface flow constructed wetland and horizontal subsurface flow constructed wetland are three kinds of phytoremediation constructed wetlands.Through the experiment design,operation field and sampling analysis,the effects of nitrogen removal from three kinds of constructed wetlands are compared.Based on the nitrogen conversion principle model,a conceptual model for the ecological dynamics of the phytoremediation of the farmland's denitrification nitrogen cycle was established.The genetic algorithm was combined with the least-squares nonlinear optimization method to use MATLAB independent programming to rate the unknown parameters in the model.Determined,then use STELLA software to simulate the nitrogen change process in the wetland system,and use the measured data to verify the model.Lysimachia christinae Hance,Trapa bispinosa Roxb,and Iris pseudacorus L.can purify the farmland water retreat.The order of their purification ability is: Iris pseudacorus L.>Trapa bispinosa Roxb>Lysimachia christinae Hance.;in the comparison of three kinds of constructed wetlands,the vertical subsurface flow constructed wetland No.2 pool has the best removal effect on TN.Temperature and pH can directly affect the removal efficiency of nitrogen in constructed wetlands;the removal rate of TN increases as the influent concentration of wetland increases.Based on the ecological dynamics model and the law of conservation of mass,an ecological dynamic model for the restoration of nitrogen in the farmland was established.The simulated effect of ammonia nitrogen,nitrate nitrogen,and organic nitrogen concentration in the effluent of No.2 pond was found.The ecological dynamic model of nitrogen cycle and the first-order kinetic model of removing TN were compared and analyzed in the simulation of the No.2 pool.It was shown that the ecological dynamic model could accurately predict the change of the concentration of effluent in the constructed wetland.The model can provide theoretical support for the design and operation of the constructed wetland and the prediction of the effluent concentration to facilitate the mastery of the actual purification effect of the constructed wetland.