Abstract: The effect of nanoTiO₂ on the mass ratio of nitrate nitrogen and activity of nitrate reductase (NR) in soils were investigated by laboratory simulation experiments. The results show that the nanoTiO₂ can reduce the mass ratio of nitrate nitrogen and the activity of NR in soil, with the increase of time, the degree of reduction increased first and then decreased. Under the same sampling time, the mass ratio of nitrate nitrogen and NR activity of nano-TiO^-2 in different types of soil decrease as follows: sandy soil>black soil>peat soil, and the degree of reduction increases with the increase of nanoTiO₂ addition. In the presence of alfalfa, nanoTiO₂ decreases the mass ratio of nitrate nitrogen and NR activity in the soil. Therefore, the nanoTiO₂ can reduce the intensity and rate of soil denitrification, and alfalfa can reduce the biological toxicity of nanoTiO₂.

Key words: nanoTiO₂, soil, nitrate nitrogen, activity of nitrate reductase