| The ammonia nitrogen pollutants in groundwater of a park in Zhejiang Linhai Province were studied.Firstly,the source and temporal and spatial variation characteristics of ammonia nitrogen pollutants in groundwater of the park were analyzed.Then,the groundwater flow model and numerical model of the park were established through GMS.On this basis,the solute transport model was established to realize the purpose of tracing ammonia nitrogen pollutants to the source.Specific achievements have been made as follows.(1)By comparing the groundwater monitoring data with the raw and auxiliary materials and groundwater organic data of the enterprises,it was found that the points of ammonia nitrogen exceeding control value were concentrated in the synthetic leather enterprises in the east of the park,and mainly concentrated in the dry and wet workshops,synthesis workshops,sewage stations and tank areas of synthetic leather enterprises.By comparing the monitoring data of 102 monitoring sites in March 2021 with the monitoring standards,a total of 68 sites in the park with ammonia nitrogen concentration exceeding the Class Ⅳ groundwater water standard in March 2021 were obtained,and the exceeding rate was 66.7%.There were 26 points exceeding the control value of 15mg/L,accounting for 25.5% of the total.The results show that the ammonia nitrogen pollution index in groundwater is high and it is affected by human.(2)According to the data,the average concentration of ammonia nitrogen in the park decreased year by year from 2018 to 2021.2021 is about 41% lower than 2018.According to the measured data of groundwater ammonia nitrogen pollution in March 2021,ArcGIS was used to generate spatial pollution distribution map.Combined with the characteristics of low hydraulic gradient in the park and the average concentration of ammonia nitrogen in 2020,it was concluded that some synthetic leather enterprises in the eastern part of the park illegally discharged waste water from January to February 2021.(3)The basic information of the park was mastered through data collection and investigation.On this basis,the conceptual model of the park was established.The numerical model of the park was established by using GMS software.The simulation results show that the variation range of groundwater level in the park is small and changes regularly year by year,and the annual peak value of water level is concentrated from May to September,which accords with the hydrometeorological characteristics of the park.The measured flow field diagram and simulated flow field diagram in April2020 were fitted with a high degree of fitting and the model establishment was more accurate.(4)The synthetic leather enterprises in the east of the park were investigated and divided into two areas according to the degree of concentration.By setting identification points in solute transport model,the pollution sources from January to February 2021 were retrieved.Three scenarios were simulated.Through continuous debugging of pollution identification points,56 pollution identification points were finally selected to simulate the pollution diffusion situation,and 4 monitoring points were selected to fit the ammonia nitrogen concentration in groundwater in March 2021,and the fitting condition was good.Therefore,according to the location and number of identification points,the enterprises on the pollution responsibility traceability.(5)A simple pollutant data management platform is designed based on open source WebGIS.The implementation method is to input the excel table containing the point names and measured values,and automatically generate the pollution distribution map in the web page.Set the excess concentration value to 150mg/L.If the concentration exceeds the standard,a prompt will be generated in the visual interface.The two situations of exceeding the standard and non-existent are simulated respectively,and the normal use can be satisfied through the actual measurement. |
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