The anisotropic molecular polarizability of the nitrate anion and its decomposition 
into atomic contributions is studied using ab initio quantum chemistry and the Atoms 
in Molecules theory. Aqueous solvation of NO3- in interfacial environments is 
investigated by a Car-Parrinello molecular dynamics simulation of a cluster, and 
classical molecular dynamics of an extended slab system with bulk interfaces using a 
polarizable force field based on the Atoms in Molecules analysis. Both in aqueous 
clusters and in systems with extended interfaces the nitrate anion clearly prefers 
interfacial over bulk solvation. This is primarily due to its large value of molecular 
polarizability, the gas phase value of which is reduced by only 5-10% in the aqueous 
environment. For polarizable force field simulations of ionic solvation, we 
recommend to cast the NO3- polarizability into three equal contributions of roughly 
1.3 A3 placed on the oxygen atoms of the anion.