Study on migration and transformation rule of farming area´s nitrogen in vadose zone taking the blown-sand region of the northern Shaanxi province for example

Taking the Blown-sand Region of the Northern Shaanxi Province for example, studying on migration and transformation rule of farming area´s nitrogen in vadose zone, this paper simulates the migration and transformation rule of farming area´s nitrogen in vadose zone with the methods of field sampling, indoor tests analysis and numerical simulation. The results showed that the content of ammonia decreased rapidly, removed down slowly and accumulated in topsoil when ammonia nitrogen entered into farming soil. Nitrite and nitrate accumulated in soil profile and migration velocity accelerated with soil water moving downwards. Moreover, the nitrogen flux increased as time went by. The simulation results demonstrated that nitrogen went into groundwater in the form of nitrite nitrogen and nitrate nitrogen, with the nitrate primarily and its transfer speed greatly influenced by lithology. This paper established the coupled model of vadose zone water and “N” migration and transformation to provide early warning platform for groundwater pollution and protection of the studying area in the future, which is of important practical significance.