| The propose of the dissertation is to study the hydrogeochemistry law of total hardness in groundwater of Beijing urban,setting up a groundwater numerical model for forecasting their evolution trend in order to provide the scientific evidence for groundwater management.The main content in the dissertation include:1.Observe the groundwater quality of study area,analysis the groundwater chemical characteristics.2.Investigate the hydrogeological process and quantificational evaluate the effect on the groundwater.3.Setting hydrogeology conception model and mathematic model.4.Setting up the three-dimensional groundwater transport model on total hardness.5.Forecast the evolution trend of total hardness by the transport model. The main method is numerical simulation,including the groundwater flow simulation. solute transport simulation and the hydrogeological transport simulation.and the dissertation also applies the geological statistics,spatial analysis on GIS.The dissertation results include:1.By one-dimensional hydrogeological transport modeling,the solute transport characteristics with respect to dilution,mineral precipitation/dissolution and ion exchange are discussed.The conclusion reveals that the mineral precipitation/dissolution and ion exchange have great influence on the concentration of ions only in initial period,and after that,the influence is trifling.Thus it is predicted that the increase reason about the total hardness is likely to the mineral precipitation/dissolution,ion exchange in vadose zone.2.Setting a three-dimensional transport model for calcium and magnesium,the model consider the convection,dispersion and isotherm sorption of calcium and magnesium,the simulation result shows that the calcium has an basic consistent extent with magnesium,and the model has an right construction and parameters.3.Dispersion is descent from western to eastern;the longitudinal dispersion of eastern monolayer is 5-10m,and 1-5m for middle layer.Retard coefficient(R) and distribution coefficient between solid and liquid are increasing from eastern to western,which are 1.02-1.05 and 4.4-5.0×10-9L/mg respectively,and 1.07-1.09 and 9.2-9.7×10-9L/mg in the middle transition belt.4.Under the conditions of the status quo,It forecast results show that:analog zone unconfined aquifer,and the southern suburb of Fengtai district to continue to increase total hardness,total hardness in southern Fengtai annual increase of 35-40mg/l around the southern suburbs of the eastern part of the total annual increase of hardness of 50-60mg/l,total hardness in the south of Beiyuan region increased the scope of expansion,the pace of expansion of about 0.25 km/y,four little change in urban areas;confined water total hardness did not change the overall trend.Diving over an area of 664.27km2,expanded 12.41km2 than that of 2006;confined aquifer over an area of439.97km2,expanded 30.31km2 than that of 2006. Under the conditions of Year-on-year emissions reduction,diving over an area of 610.14km2,reduced 41.72km2 than that of 2006,confined water reduced 57km2 than that of 2006.Southern suburb of Fengtai and increased the range of total hardness decreased,total hardness in southern Fengtai annual increase of 25-30mg/l around the southern suburbs of the eastern part of the total annual increase of hardness of 35-40mg/l,total hardness of confined aquifer changed little.5.In the Simulation area,the high hardness areas including Dongba,Xianqiao Shaxianqiao,the southern suburbs and some areas of the Daitou,which is a large total Fengtai district,west of the structure of single-layer aquifer areas and densely populated urban areas.Dongba and the southern suburbs of the region may be groundwater irrigation has led to the increase in total hardness,Fengtai intensive industries total hardness of groundwater in the area have increased the impact of groundwater as a result of the western region is a single-layer structure,and therefore vulnerable to man-made pollutants enter impact.In addition to the above reasons of human activity,the role of hydro-geochemical,especially in the vadose zone,the mineral dissolution of groundwater plays an important contribution to total hardness.
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