Migration and transformation rule of nitrogen in vadose zone and groundwater: A case of Hebei plain

To reveal the migration and transformation rule of nitrogen in the vadose zone and groundwater and to determine the migration mathematical model, we researched the migration and transformation rule of ammonia nitrogen, nitrate nitrogen, nitrite nitrogen in the vadose zone and groundwater by the soil column leaching experiment. The results indicate: using ammonium bicarbonate shows a stronger alkalinity to the soil than using the urea; nitrogen pollution in the vadose zone and groundwater is mainly caused by the ammonia nitrogen; nitrate nitrogen in vadose zone is easier to move with the flow, that is to say, ammonia nitrogen adsorption is greater than nitrate nitrogen adsorption. This migration model can calculate quantitatively and predict the temporal and spatial distribution of concentration of nitrogen in the vadose zone and groundwater.