Transformation Of Soil Nitrogen Under Ultraviolet Radiation

Nitrogen cycling, which is the today’s research hotspot, plays an important role in ecosystem stability and development. Photochemical conversion of nitrogen is one of the important paths of nitrogen geochemical circulation. In this study, the effects of soil thickness, reaction time, amount of nitrate dose, pH, light intensity on the photochemical transformation of soil inorganic nitrogen (NH4+, NO3- and NO2-) and dissolved organic nitrogen (DON) were studied by means of a self-made photochemical reactor, In addition, the ultraviolet irradiation conversion phenomena of NH4+, NO3- and NO2- in solution with and without the inorganic minerals were also studied. The main results are as follows:1. When the initial reaction solution, only the presence of NO3-, the light converted NO3-to NO2-. NH4+ in the initial reaction solution under the light, converted to the NO3- and NO2-. In all systems NO2- concentration with increased illumination time increased significantly.2. The greater the UV intensity, the longer the exposure time, the more significant phenomenon of the transformation of inorganic nitrogen forms. UV irradiation increased the soil DON and DOC.3. Light on the different size of soil organic carbon and nitrogen and various forms of inorganic nitrogen was not significant. The thinner the layer, light to promote formation NH4+ and NO3- in phenomenon is more significant; the thicker the layer, the phenomenon of that light to promote formation NO2- is more significant.4. The increasing of soil moisture can promote soil NH4+ and NO2- formation; in a weak acidic condition, the illumination is the greatest impact to the soil nitrogen transformation; in a strong acid and strong base condition, release inorganic nitrogen in free state.5. The existence of NO3- makes the increase of DOC and NH4+ under the illumination, and the emergence of NO3- was significantly decreased in the phenomenon; and adds a high dose of NO3- inhibited soil light convert to DOC and NH4+, and NO3- reduction is not significant.