Water Quality Simulation And Visualization Of Typical Rare Earth Mining Areas In The Upper Reaches Of Ganjiang River Basin Based On WASP Model

With the rapid development of economy in Ganjiang River basin,the rapid rise of rare earth mining industry,the enhancement of agricultural intensive degree and the increase of population,the water environment pollution is becoming more and more serious,which has affected the normal life of the surrounding residents.Based on WASP model and GIS spatial analysis,land use classification and pollution load accounting,the ammonia nitrogen in Longnan County,a typical rare earth mining area in Ganjiang River Basin,is simulated in this paper.The water quality pollution status of total nitrogen is analyzed,the parameter sensitivity of each pollution index is analyzed,the uncertainty of non-point source pollution load is discussed,and the map output function and spatial analysis function of(GIS)are applied.Visual display of water quality results and determination of key polluted river sections in Ganjiang River Basin are realized,which provides scientific basis for water pollution control strategy of typical rare earth mining areas in Ganjiang River Basin.The main research contents and results are as follows:(1)Based on the hydrology,water quality and the measured data of the typical coal mine area in the Ganjiang river basin,the water quality model of the water area of the Longnan County is constructed by using the WASP water quality model,and the non-point source pollution load caused by the rare earth mining in the research area is comprehensively considered in the pollution load,By using the improved output coefficient model,the land-use classification method,the spatial analysis of GIS,the determination of the output coefficient and the site investigation of the pollution source are used to estimate the pollution load of the non-point source in the Longnan County.(2)Using the constructed WASP water quality model,the measured data from January 2016 to May 2017 were used as sample data to calibrate the parameters of ammonia nitrogen and total nitrogen in Longnan County water area,and some important parameters were obtained.The relative error of the simulation results of the two indexes is less than 30%,the consistency is above 0.85 and the linear fitting degree is above 0.9.The variation trend of pollutant concentration is more consistent with the measured value.(3)Based on the WASP water quality model,the sensitivity analysis of the mainparameters of ammonia nitrogen and total nitrogen was carried out.The results show that the sensitive parameters of ammonia nitrogen are nitrification rate constant at20 ?,organic nitrogen mineralization rate at 20 ? and denitrification rate constant at20 ?.Nitrification temperature coefficient,denitrification temperature coefficient and organic ammonia mineralization temperature coefficient were the second,and the sensitive parameters of total nitrogen were approximately the same as ammonia nitrogen.Three different pollution scenarios are set up to compare and analyze the uncertainty of non-point source pollution load in this area.The results show that the effects of various non-source pollution sources on the simulation accuracy of the model are as follows: increasing the amount of chemical fertilizer application >increasing the mining land > increasing the number of population,respectively.The effect of increasing fertilizer application rate on total nitrogen was the most obvious,and the most obvious effect on ammonia nitrogen was caused by increasing the pollution caused by mining land entering the river.(4)The simulation results of ammonia nitrogen and total nitrogen are visualized by using the method of GIS technology and WASP model external integration.According to the statistical analysis function of ArcGIS,the river length ratio of two kinds of indexes and different water quality in the study area is obtained.The results show that the ammonia nitrogen of different water bodies in the basin.Between January 13,2016 and May 20,2017,the proportion of total nitrogen reached to the inferior category was 25% to 40%,63% to 90% respectively,and the annual average concentration of the basins with inferior ? accounted for 50% and 75%,respectively.The pollution degree of the main channel is: Lianjiang River > Wojaing River >Taojiang River > Taiping River.