| The Baoshan Basin has a large population and is one of the industrial and agricultural development areas in Baoshan City.People have high requirements for the quality and quantity of groundwater.However,human production and living activities have caused serious pollution to the shallow Quaternary groundwater in the basin,which threatens human health and restricts the development of local society and economy.Therefore,it is particularly necessary to comprehensively investigate the hydrochemical characteristics and genesis of the Quaternary shallow groundwater in the Baoshan Basin,as well as groundwater quality evaluation and pollutant migration rules.Taking the Quaternary shallow groundwater in Baoshan Basin as the research objective,this paper uses EVS three-dimensional geological modeling software to establish the Quaternary three-dimensional visualization geological model of the basin,and divides the Quaternary shallow groundwater aquifer of the basin into three independent groundwater systems based on the model display results: Banqiao-Hetu groundwater system(?),Xiacunjie-Hanzhuang groundwater system(?),Xialongtan groundwater system(?).According to the divided groundwater systems,it is concluded that the groundwater chemistry types in the basin are mainly HCO3-Ca?HCO3-Ca·Mg by drawing the Piper three-line diagram;Gibbs diagram,ion scale coefficient,and chlor-alkali index show that the hydrochemical characteristics of shallow groundwater in the Quaternary in the basin are mainly controlled by the dissolution of carbonate and silicate rocks.Groundwater quality evaluation results show that iron,manganese,and ammonia nitrogen are the main excess ions in the study area,and the excess range of iron and manganese has a high degree of consistency;a total of 28 sample points meet the quality standards of groundwater III,accounting for 80% of the total number of water samples;Seven sample points exceeded the groundwater Class III standard,accounting for 20% of the total number of water samples.Using GMS to study the pollutant migration law of ammonia nitrogen and manganese,the results show that the movement of the ammonia nitrogen pollution halo in the basin is mainly controlled by convection,dispersion and pollution sources,and the ammonia nitrogen pollution halo actually migrates to the east and west along the direction of the water flow.The relationship between distance and time is =1 × 10 + 0.0167-1.69,S = 2 × 10 + 0.0265-0.78,and the control distances of pollution sources on the east and west sides are 1.69 m and 0.78 m respectively.The migration impact caused by pollution sources on the west side is lower than that on the east side.The movement of the manganese pollution halo in the basin is mainly affected by convection and dispersion.The relationship between the actual migration distance and time on the east and west sides of the manganese pollution halo along the water flow direction is S = 8 × 10 + 0.0292,S =9 × 10 + 0.0317.The ammonia nitrogen and manganese pollution halo centers in the basin will shrink towards the Donghe River over time,and the maximum concentration of the pollution halo will gradually decrease,which indicates that convection plays a dominant role in the process of pollutant migration.In addition,As time goes by,the influence of convection in the process of pollutant migration will gradually increase,and the influence of dispersion will gradually decrease.Since the hydraulic gradient on the west side of the basin is greater than that on the east side,the same pollution concentration value migrates longer in the direction of the larger hydraulic gradient,so the actual migration distance on the west side of the pollution halo along the water flow direction is always higher than that on the east side. |
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