Suburbs Of Beijing, Groundwater Nitrate Nitrogen And Total Hardness Hydrogeochemical Processes And Numerical Simulation,

The propose of the dissertation is to set up three-dimensional groundwater transport numerical model on the total hardness and nitrogen in Beijing urban, and forecast their evolution trend in order to provide the evidence for groundwater management.The main content in the dissertation include:1. Summarize the evolution characteristics of the total hardness and nitrogen;2. Investigate the hydrogeochemical process including mineral precipitation/dissolution, ion exchange and denitrification, and quantificational evaluate the effect on the groundwater.3. Set up the three-dimensional groundwater transport model on total hardness and nitrogen, and4. Forecast the evolution trend of total hardness and nitrogen 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 and the hydrogeological ratio coefficient.The dissertation results includes:1. The sources of the primary ions of groundwater in Beijing urban were discussed by the methods of the variance analysis and ratio-coefficient. The main conclusion illustrate that NO₃^- and Cl^- come from the anthropogenic discharge, and Ca²⁺, Mg²⁺ and HCO₃^- comes from mineral dissolution. The hydrogeochemical processes with respect to hardness and nitrogen are mineral precipitation/dissolution, ion exchange and denitrification.2. By one-dimensional and two-dimensional hydrogeological modeling, the solute transport characteristics with respect to recharge, 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.3. The first-order coefficient of denitrification is estimated by the observed data of the nitrogen plume, and4. The three-dimensional groundwater transport model on the total hardness and nitrogen in Beijing urban is achieved.The innovation in the dissertation may be:1. Advanced new estimate method about the first-order dynamic coefficient of the denitrification in urban.2. The application of the two-dimensional hydrogeological modeling, and3. The application of variance analysis to judge anthropogenic influence on chemical composition of groundwater...