Synchrotron-based high-resolution photoemission and X-ray absorption near-edge spectroscopy (XANES) have been used to study the interaction of SO2 and NO2 with ZnO(0 0 0 1)-Zn and polycrystalline surfaces of zinc oxide (films and powders). Important differences are observed when comparing the chemical behavior of the adsorbates on these oxide surfaces. These differences are in part a consequence of changes in structural properties (flat versus rough surfaces), but in some cases they clearly originate in variations in surface composition (zinc tt adsorbate versus oxygen tt adsorbate interactions). For example, the Zn-terminated (0 0 0 1) crystal face of ZnO is much less reactive towards SO2 than polycrystalline ZnO. On ZnO(0 0 0 1)-Zn and polycrystalline ZnO, the Zn <-> SO2 bonding interactions are weak. Adsorption of SO2 on Zn sites was seen only at temperatures below 200 K. In contrast, the SO2 molecules react readily with O sites of Ar+ sputtered ZnO(0 0 0 1)-Zn or polycrystalline ZnO forming very stable SO3 species. Due to its radical nature, adsorbed NO2 is more chemically active than SO2. After dosing nitrogen dioxide to ZnO(0 0 0 1)-Zn at 100 K, chemisorbed NO2 and NO3 coexists on the surface. A partial NO2. ads --> NO3, ads transformation is observed from 150 to 300 K. The data for the NO2/ZnO(0 0 0 1)-Zn system clearly prove that large quantities of NO3 can be formed on metal sites of an oxide surface as a consequence of partial decomposition or disproportionation of NO2. The routes for the formation of SO3 and NO3 on ZnO can be different, but these species have in common a high stability and decompose at temperatures well above 500 K. Thus, ZnO powders can be useful as sorbents in DeSO(x) and DeNO(x) operations.