Temperature programmed depletion (TPD) was performed for both surface nitrates (H+-NO3-) and surface nitrites (H+-NO2-) on Na-Y. The depletion curves are each adequately described with a pre-exponential of 10(13) and activation energies that vary as a function of coverage from similar to 100 to 200 kJ mol(-1). Multiple adsorption sites could lead to the observed variation in activation energies. NO2- is more kinetically stable than NO3- on Na-Y. The effect that the method of preparation of NO3- and NO2- could have on the relative stabilities of the nitrates and nitrites is discussed. The trends for the relative stabilities of different nitrates and nitrites on Na-Y and BaNa-Y are examined as a function of the cationic adsorption site and the counter-ion (e.g., H+ and NO+). The possible roles of the stabilities of nitrates and nitrites in low temperature DeNOx catalysis are considered. (C) 2009 Elsevier B.V. All rights reserved.