A Preliminary Study On The Dynamics Of Nitrogen Transport And Transformation In Soils Under The Conditions Of Irrigation With Sewage Effluent And Fertilization

Studying on the mechanism of nitrogen transport and transformation under the conditions of fertilization and irrigation with sewage effluent is very important for utilization of sewage effluent and fertilizer and pollution control. Based on laboratory and field experiment and numerical simulation, nitrogen transport and transformation has been investigated in this dissertation. In laboratory study, the experiments of NH/桸 transport and transformation has been conducted with columns packed with homogeneous sandy loamy under saturated and unsaturated conditions. Meanwhile the adsorption pattern of NH4" has been studied with batch equilibrium method. Results indicate that the transport of NH4*桸 in soils shows significant retardation, and the adsorption pattern of NH4+ can be described with linear model. It is also shown that NH4+-N exists slight and much more nitrification phenomenon in saturated soils and unsaturated soils respectively. And NO3 --N can be leached to soil layer below die wetting depth.The convection-dispersion equation with the retardation coefficient yield by method has been adopted to model NH4--N transport in saturated soil, simulation results are compared well with experimental results.In field study ,the expenment on nitrogen transport and transformation in soils with different irrigation (with both ground water and sewage effluent) and fertilization levels has been conducted. With considenng the N-uptake, nitrification and demtrification processes, a model for describing NO2--N transport and transformation in unsaturated soil has been applied. Results show that, the N03+-N accumulating in soil is contributed more by fertilization but lees by irrigation with sewage effluent, and the model can be used to simulate NO3- - N transport in soils.