Simulation Study on the Nutrient Purification Effect of Vegetation Coverage in Artificial Wetlands
Based on the mechanisms of wetland water purification such as plant flow resistance,oxygen secre-tion,and the absorption of nutrients by plants and microorganisms,the"WQ nutrition+vegetation"wetland model was established using the custom and editing functions of the EcoLab water quality module in MIKE21.This model was coupled with the hydrodynamic module in MIKE21 to create a water quality-hydrodynamic mod-el.On the basis of field research on the artificial wetland of Wujiadui,the water quality-hydrodynamic model was applied,considering the distribution and coverage of plants,to study the effect of artificial wetland plants on water purification.Key parameters of the role of wetland plants in water quality were calibrated using actual measured data from the Daguan River and Duanqiao cross-section,and the simulation results were verified.The results show that after planting vegetation,the concentrations of TP,TN,and NH4+-N inside the wetland are lower than those in the Daguan River.The concentrations are not only affected by the vegetation coverage but al-so by the water flow rate.A higher flow rate can effectively increase the reoxygenation capacity of the water sur-face and accelerate the water purification effect.As the plant coverage increases,the degradation rate of TP,TN,and NH4+-N gradually decreases.When the vegetation coverage is between 20％and 30％,the purifica-tion efficiency of TP and TN is relatively high,with the highest values reaching 6.39％and 0.2％,respectively.When the vegetation coverage increases to 40％,the flow rate drops significantly,the water-blocking effect of the vegetation is markedly enhanced,the reoxygenation capacity of the water body is weakened,and the purifica-tion efficiency decreases.Under different vegetation coverage rates,the purification rates of NH4+-N and TP are relatively high,and the NH4+-N purification rate is basically consistent with that of TN,indicating that NH4+-N is the main factor affecting the purification efficiency of TN.A comprehensive analysis of the water qual-ity concentrations and purification efficiencies of TP,TN,and NH4+-N under different wetland vegetation cover-age rates indicates that a plant coverage rate between 20％and 30％is more suitable for the study area of the Wujiadui artificial wetland.
constructed wetlandMIKE 21-EcoLabwater quality simulationpurification function of vegeta-tion
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