Nitrate Radical Cannot Initiate Oxidation of Hg(0) to Hg(II) in the Laboratory or at Ground Level in the Atmosphere

Multiple field studies have led to suggestions that nitrate radical (NO3) participates in oxidizing gaseous Hg(0) in the atmosphere. These suppositions are hard to reconcile with the two-step mechanism of Hg(0) conversion to Hg(II) via Hg(I), due to the instability of the NO3-Hg(I). We use a high level of computational chemistry to determine its bond energy as 6.5 kcal mol-1. We use statistical mechanics to compute the equilibrium constant, Kc(T) for NO3 + Hg(0) = NO3Hg(I), and a box model to investigate a field study and laboratory kinetic investigation of this chemistry. Under the conditions of the one field study showing a correlation between [NO3] and [Hg(II) (g)] , NO3 could not have contributed significantly to the formation of Hg(II). In addition, we find that the one experimental kinetic study of this reaction does not constrain the rate constant.