Cultivated Land Changes Have An Impact On The Plains Of Baiyangdian Watershed Research On The Influence Of "Three Nitrogens" In Groundwater

In recent years,the rapid development of industry and agriculture in our country.But the excessive exploitation of groundwater,the extensive use of farmland fertilizers,and the direct discharge of domestic sewage have caused the groundwater level in the plains of the Baiyangdian River Basin to drop drastically,forming multiple large funnels and increasing the concentration of nitrate in the groundwater.Environmental problems are prominent,posing potential threats to the construction of Xiongan New Area.Based on the national key research and development project,"Xiong’an New Area t Groundwater Environmental Risk Prediction,Early Warning and Prevention and Control Project",this paper takes the Baiyangdian River Basin plain area as the research object,and comprehensively uses data collection,field investigation,hydrogeological survey,and groundwater flow numerical value simulation and other methods analyze the temporal and spatial evolution characteristics of the groundwater dynamic field and chemical field in the study area,the simulation predicts the movement law of "three nitrogens" in groundwater.Combined with the planning of the new district,the impact of the change of cultivated land on the groundwater environment was predicted..The main achievements are as follows:(1)The land use in the study area is dominated by agricultural land,accounting for 52.11%,followed by residential land and forest land,accounting for 17.38% and 12.10% respectively.Human activities and government policies strongly control the diversity and heterogeneity of the landscape,and the land use landscape tends to be regularized and decentralized as its abundance increases.(2)The main pollutant of groundwater in the study area is nitrate.The spatial distribution of nitrate pollution is higher in the northwest and lower in the southeast,and the piedmont alluvial lake plain is higher in the eastern lacustrine plain.They are mainly distributed in dense urban areas and towns with relatively large arable land,which basically coincides with the use of chemical fertilizers and population density.(3)Combined hydrogeological conditions and based on GMS,build a three-dimensional groundwater flow and solute transport model in the study area.Through the identification and verification of the model,the constructed model conforms to the actual situation in the study area,meets the accuracy requirements,and proves that the model is reliable.(4)According to the "Baiyangdian Ecological Protection Plan" and "Hebei Xiong’an New Area Planning Outline",we designed a water supplement scenario and four land-use change scenarios to predict the changing trend of nitrate ion concentration in groundwater,and the forecast period is 15 years.Scenario one is to carry out ecological water replenishment.Under the condition that the land use remains the same for the current year,although the water level of Baiyangdian Lake and the water level of the landing funnel are rising rapidly,the area of Class III water is gradually expanding,and the water quality is in deteriorating state.Scenario2 is to increase the population of Xiongan New Area on the basis of Scenario 1,and the water quality further deteriorates.Scenario 3 is to reduce the area of cultivated land in Xiongan New Area,the concentration of nitrate nitrogen has been steadily reduced,and the water quality has been significantly improved.Scenario 4 is to reduce the amount of fertilization in the study area on the basis of Scenario 3 and improve the efficiency of domestic sewage treatment.The rate of decrease of nitrate concentration increase significantly,but there are still some places where the groundwater quality exceeds the standard.It shows that taking water supplement measures while reducing the area of arable land,controlling the amount of fertilization,and reducing the discharge of domestic sewage can effectively improve the quality of groundwater.(5)By the prediction results and considering the characteristics of the groundwater environment in the study area,measures such as water transfer,water-saving,planting lowwater-consumption crops,reducing the area of arable land,and reducing the use of chemical fertilizers can ensure the future supply of water resources in the new area to a certain extent and prevent the deterioration of groundwater quality.However,nitrate pollution in Rongcheng is still serious,and remediation measures need to be taken in this area.The anti-pollution performance of groundwater in the mountain piedmont area is relatively good,and pollutants are easy to enter the groundwater.It is necessary to reform the enterprises that have pollution risks.