Hydrogeochemical Simulation Research On Groundwater Evolution Of Luohe Aquiferous Group In The South Area Of Ordos Basin

Groundwater evolution is a foreland and hotspot in the fields of international hydrogeology and environmental science,which depicts hydrogeochemical zones and sorts of hydrogeochemical processes mainly through researching space-time distributing rules of groundwater chemical characters. Such a research also helps redintegrate and forecast the geochemical evolution process in a groundwater system.The cretaceous groundwater quality is very complex in Ordos basin. It is possible to research this geochemical field with the theory of hydrogeochemical simulations. Such a research is of significance for finding out the groundwater storage characters and the conditions of recharge ,runoff and drainage in this region. It is alse helpful to evaluate the regional groundwater resource and its exploitative potential. Therefore, there is no doubt to play important roles in accelerating the regional economic development and facilitating environmental protection.In this article, first of all, the auther summarily introduces the source of the selected title of this thesis and its significance of the research,in which the current situation in this research field is expounded. The main research content and the research approach of the thesis are as well as indicated. Then the theory of hydrogeochemical simulation is dissertated,which includes the speciation calculation, mass balance simulation, reaction-path simulation, the corresponding mathematic models and their numerical methods. In addition, the application approachs of hydrogeochemical simulation are also illuminated. In succession, this article thoroughly researchs the geology, physiognomy, hydrogeology condition of Ordos basin cretaceous Luohe aquiferous group in the south of Baiyu mountain. Based on the item of Groundwater Survey of Ordos Basin from China Geological Survey (CGS), the article does a research on the regional groundwater evolution and the mechanism of groundwater forming with a series of hydrogeochemical simulations ,several conclusions are obtained:(1)The mass balance simulation keeps a better consistence with the reaction path simulation in the calculation of hydrogeochemistry,which illuminates the feasibility of integrating the two methords. And it is helpful to use the reaction path simulation to validate the result of the mass balance simulation. According to the tendency of reactions, the reaction path simulation can estimate and forecast the environment of groundwater.(2)This research proves that the Malian river valley is not only the catchment area of the surface water but also the drainage area of the deep groundwater.So it should be the base level of drainage in the artesian basin.(3)Although most of the water quality data are abbrevialed analyses and some total analyses without full analysed items, yet typical minerals can still be used to research the basic water-rock interaction.Therefore, the minerals used are calcite, dolomite ,gypsum, halite, sylvite, Ca2+ (Mg2+) /Na+ ion exchange and Ca2+/Mg2+ ion exchange. Combining the analyses of selected hydrogeochemical parameters,it may be considered that the main process controlling the evolution of natural groundwater is the dissolving of gypsum and halite and the precipitating of calcite in the west of Ziwu mountain.In some areas ,dissolving incongruently of calcite and dolomite occurs.The ion exchanges among Ca2+,Mg2+,and Na+ should not be ignored.(4)Because the water samples of Q3,N3,HK1,B12 are total analyses,flow path Q3-N3 and HK1-B12 are calculated under the system of silicate- aluminate.The result shows that the minerals that controlling the evolution of natural groundwater along the two flow paths are calcite, gypsum, halite, feldspar,mica , fluorite, chalcedony,illite,kaolinite , and ion exchange among Ca2+,Mg2+,and Na+. Consequently,the water-rock interaction controlling the evolution of groundwater in the south of Baiyu mountain,especially in the Malian river valley should be similar to that of Q3-N3.(5)The watershed of groundwater in the south of Ziwu mountain(close to the flow path of HK1-B12) is not that of surface water. The watershed of groundwater ought to at least lie in the site of HKl.That is to say the watershed of groundwater should move east 12 km relative to that of surface water.(6)The simulation calculation of ZX2-S13 indicate that a transition between recharge area and runoff-drainage area is obvious along this flow path,so do the hydrogeochemical zones.At least,the coherence between the recharge and drainage is shown between the groundwater and the surface water in the transition to Luohe river valley.Meanwhile,it is indicated that evaporation plays an important role during the evolution of groundwater.In conclusion , this article sums up the hydrogeochemical simulations of Ordos basin cretaceous Luohe aquiferous group in the south of Bai yu mountain based on the foregoing discussions, and makes a forcast.