Regional Characteristics of Atmospheric Sulfate Formation in East Antarctica Imprinted on ¹⁷ O?Excess Signature

17O-excess (?17O = ?17O ? 0.52 × ?18O) of sulfate trapped in Antarctic ice cores has been proposed as a potential tool for assessing past oxidant chemistry, while insufficient understanding atmospheric formation around Antarctica hampers its interpretation. To probe influences regional specific we compared year-round observations ?17O non-sea-salt aerosols (?17O(SO42?)nss) at Dome C and Dumont d'Urville, inland coastal sites East Antarctica, throughout the year 2011. Although ?17O(SO42?)nss both showed consistent seasonality with summer minima (?1.0‰) winter maxima (?2.5‰) owing to sunlight-driven changes relative importance O3 oxidation OH H2O2 oxidation, significant intersite differences were observed austral spring–summer autumn. The cooccurrence higher (2.0‰ ± 0.1‰) than site (1.2‰ chemical destruction methanesulfonate (MS–) during (October–December), combined first estimated ?17O(MS–) ?16‰, implies that MS– produces high ?12‰. If contributing known postdepositional decrease snow, this process should also cause increase over 1‰, can reconcile discrepancy between atmosphere ice. autumn (March–May) may be associated involving reactive bromine and/or sea-salt particles region.