Radiolysis of Water Containing Dissolved Nitrogen Species

Abstract

The effects of dissolved nitrate on the gamma radiolysis of water were studied at an absorbed dose rate of 2.1 Gy⋅s^-1 at room temperature. Air- or argon-saturated nitrate solutions at pH 6 and 10.6 were irradiated, and the aqueous concentrations of molecular radiolysis products, H₂, H₂O₂, NO₃^-, and NO₂^-, were measured as a function of irradiation time. The experimental results were compared with computer simulations using a comprehensive radiolysis kinetic model. The radiolytic process of nitrate occurs mainly through interactions with radical species generated by water radiolysis, •e_aq^-, •O₂^- and •OH. The kinetic analyses using smaller reactions sets indicate that measured H₂ and H₂O₂ can be used to calculate radical concentrations and provide information on the redox conditions of irradiated aqueous solutions. Model data and experimental analyses show that the presence of 10^-3 M nitrate increases [H₂O₂] and [H₂] at the expense of the related radical species and also increases the time required to reach steady state relative to the pure water case.