Temperature dependence of hydrogen atom reaction with nitrate and nitrite species in aqueous solution

Arrhenius parameters for the reaction of hydrogen atoms with NO3-, HNO2, and NO2- in aqueous solution have been determined by the use of pulse radiolysis and electron paramagnetic resonance free induction decay attenuation measurements. At 25.0 degrees C, the calculated rate constants for these compounds are (5.61 +/- 0.51) x 10(6), (3.86 +/- 0.09) x 10(8), and (1.62 +/- 0.05) x 10(9) dm(3) mol(-1) s(-1) respectively, with corresponding activation energies of 48.7 +/- 1.0 (15.2-84.5 degrees C), 21.54 +/- 0.69 (5.9-62.8 degrees C) and 15.59 +/- 0.36 (6.2-86.8 degrees C) kJ mol(-1). Computer modeling of these systems suggests that . H atom reaction with either anion directly produces hydroxide anion and the corresponding NOx radical.