Oxygen has three stable isotopes (16O, 17O and 18O). Enrichment of 17O relative to the dominant 16O is normally about half of that of 18O for various physicochemical processes, except for ozone (O3) production, which uniquely enriches 17O. This anomalous enrichment of 17O (Δ17O) is inherited by other photochemical oxidants and oxidation products derived from the precursor ozone through various atmospheric oxidative pathways. Thus, the oxygen isotopic compositions of sulfate (SO42-) and nitrate (NO3-) fluctuate seasonally, but the extent to which these seasonal changes are related to changes in isotopic compositions of ozone or to contribution of other photochemical oxidants is unknown. This can only be established by simultaneous measurement of oxygen isotopes in nitrate, sulfate, and ozone from the present-day Antarctic atmosphere. However, there is a paucity of such data, and the complex chemistry is only partly understood.