Regional characteristics of atmospheric sulfate formation in East Antarctica imprinted on 17O-excess signature
Authors: Ishino Sakiko , Hattori Shohei , Legrand Michel , Chen Qianjie , Alexander Becky , Shao Jingyuan , Huang Jiayue , Jaegle Lyatt , Jourdain Bruno , Preunkert Susanne , Yamada Akinori , Yoshida Naohiro , Joel Savarino 
Published: March 2021

&lt;p&gt;&lt;sup&gt;17&lt;/sup&gt;O-excess (&lt;em&gt;&amp;#916;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O = &lt;em&gt;&amp;#948;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O &amp;#8722; 0.52 &amp;#215; &lt;em&gt;&amp;#948;&lt;/em&gt;&lt;sup&gt;18&lt;/sup&gt;O) of sulfate trapped in Antarctic ice cores has been proposed as a potential tool for assessing past oxidant chemistry, while insufficient understanding of atmospheric sulfate formation around Antarctica hampers its interpretation. To probe influences of regional specific chemistry, we compared year-round observations of &lt;em&gt;&amp;#916;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O of non-sea-salt sulfate in aerosols (&lt;em&gt;&amp;#916;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O(SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;#8722;&lt;/sup&gt;)&lt;sub&gt;nss&lt;/sub&gt;) at Dome C and Dumont d&amp;#8217;Urville, inland and coastal sites in East Antarctica, throughout the year 2011. Although &lt;em&gt;&amp;#916;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O(SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;#8211;&lt;/sup&gt;)&lt;sub&gt;nss&lt;/sub&gt; at both sites showed consistent seasonality with summer minima (~1.0 &amp;#8240;) and winter maxima (~2.5 &amp;#8240;) owing to sunlight-driven changes in the relative importance of O&lt;sub&gt;3&lt;/sub&gt;-oxidation to OH- and H&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;2&lt;/sub&gt;-oxidation, significant inter-site differences were observed in austral spring&amp;#8211;summer and autumn. The co-occurrence of higher &lt;em&gt;&amp;#916;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O(SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;#8211;&lt;/sup&gt;)&lt;sub&gt;nss&lt;/sub&gt; at inland (2.0 &amp;#177; 0.1 &amp;#8240;) than the coastal site (1.2 &amp;#177; 0.1 &amp;#8240;) and chemical destruction of methanesulfonate (MS&lt;sup&gt;&amp;#8211;&lt;/sup&gt;) in aerosols at inland during spring&amp;#8211;summer (October to December), combined with the first estimated &lt;em&gt;&amp;#916;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O(MS&lt;sup&gt;&amp;#8211;&lt;/sup&gt;) of ~16 &amp;#8240;, implies that MS&lt;sup&gt;&amp;#8211;&lt;/sup&gt; destruction produces sulfate with high &lt;em&gt;&amp;#916;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O(SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;#8211;&lt;/sup&gt;)&lt;sub&gt;nss&lt;/sub&gt; of ~12 &amp;#8240;. If contributing to the known post-depositional decrease of MS&lt;sup&gt;&amp;#8211;&lt;/sup&gt; in snow, this process should also cause a significant post-depositional increase in &lt;em&gt;&amp;#916;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O(SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;#8211;&lt;/sup&gt;)&lt;sub&gt;nss&lt;/sub&gt; over 1 &amp;#8240;, that can reconcile the discrepancy between &lt;em&gt;&amp;#916;&lt;/em&gt;&lt;sup&gt;17&lt;/sup&gt;O(SO&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;2&amp;#8211;&lt;/sup&gt;)&lt;sub&gt;nss&lt;/sub&gt; in the atmosphere and ice.&lt;/p&gt;