Research Of The Impact Factors About Nitrate Migration And Transformation Through Aquitard

With the rapid development of modern industry, the emission of pollutants is increasing, so that surface water and groundwater pollution is more serious and water quality is out of the standard. Improving people's living standards encourage people to higher quality and quantity, resulting in shortage of water resources has become increasingly serious. As serious pollution of shallow groundwater was not exploitation, over-exploitation of deep water caused the water level dropped, formation of depress groundwater cone, so that poor water quality of shallow groundwater flow through the permeable layer is deep groundwater recharge, leading the deep groundwater quality deteriorated.This study is supported by Natural Science Foundation of China. Based on domestic and international concern and it flows in shallow groundwater nitrate migration through aquitards deep groundwater pollution hot spots, the Simulation Experiment:Study under natural conditions, different pH conditions, under different Eh conditions and different sulfate concentrations of nitrate migration through the aquitard into other relevant channels and with the interaction between anions; Research aquitard interdiction capacities for nitrate and nitrate migration in the aquitard mechanism and hydrodynamic equations; established nitrate in aquitard in the migration model. Obtained the following conclusions:(1)Simulate natural conditions, the process of nitrate migrated through the aquitard under different pH, Eh, sulfates and anions interaction:The law of nitrates in different conditions thougn aquitard is similar, but slightly different. Found in the sulfate concentration is more favorable aquitard block nitrate, the second is by the impact of Eh, and finally is under different pH conditions; aquitard conversion of nitrate to the denitrification pathway is Lord, there will be very few dissimilatory reduction of nitrate to ammonia role; Under natural conditions, other related ions on the nitrate effect through aquitards is the same, but according to environmental characteristics (environmental indicators) is different, the impact has different.(2)Aquitard interdiction capability of nitrate and intercept mechanism:aquitard interdiction of nitrate is very strong, and its ability:under the conditions of different concentrations sulfate> under different Eh> different pH conditions> natural attenuation; aquitard block nitrate is strong for several reasons:Most of the pores in the aquitard to is micro-porosity, permeability coefficient is smaller and denser aquitard, so the filter mechanical role in aquitard is strong;Pores filled with water, porous gap ion interaction with solid surface enhanced; aquitard of the specific adsorption of Ca2+ can not only change the variable on the soil surface positive charge, or can make a positive constant charge colloids increase or reduce the charge negative charge, so that the negative charge on the clay surface, electrostatic repulsion decreased NO3-; clay surface adsorption lattice of hydration Ca2+ reduced the activity of clay near the water so that water diffusivity decreased, nitrate Salt migration rate also decreases, the surface water layer of clay viscosity of water, Ca2+ in the formation of positive charge layer near the clay on the NO3- produced electrostatic force, also remain in the nitrate in aquitard. At the same time there is also less permeable layer adsorption (coordination adsorption), the existence of this effect makes the aquitard adsorption of nitrate and a mechanism of increased.(3)the establishment of nitrate in aquitard in the migration model:based on the experimental data, parameters of model can be calculated. Solute transportation model is established to simulate concentration change of nitratr by mathematical model transform. The model and parameter description interception is main role of nitrate attenuation though aquitard,followed by biological effects.The simulation result fits the experimental result well by simulated groundwater conditions,it can predict the nitrate change in the aquitard to a certain extent.Through the study, a more comprehensive understanding of nitrate in aquitard and concentration in the changes of migration and transformation, in order to prevent nitrate pollution of deep groundwater and protection deep groundwater,and provides a theoretical basis and foundation for restoration of environment.