[en] The kinetics of NO₂^- ions accumulation in the 4 M aqueous acetate sodiu.m nitrate solution and its dependence on the presence of NO₂^-ion acceptors and OH radicals at the photolysis, radiolysis and photoradiational action are studied. In the presence of reagents combining NO₂^- ions in statu nascendi the value of G/NO₂^-/ increases two-fold at the radiolysis, While at the photolysis of aqueous sodium nitrate the magnitude of PSI/NO₂^-/ it does not change. The rate constant of NO₂^- ion annihilation after UV-illumination exceeds nearly twice that observed at the γ-irradiation. Possible differences in the reverse reactions at the radiation chemical and photochemical reduction of nitrate into nitrate in the cincentrated nitrite solutions are discussed