Seasonal changes in stable nitrogen isotopic composition in fine aerosols at a rural background station Ko&amp;#353;etice (Central Europe).

Petr Vodička,Kimitaka Kawamura,Jaroslav Schwarz,Vladimír Ždímal,Bhagawati Kunwar

doi:10.5194/egusphere-egu2020-3469

Abstract

&lt;p&gt;The stable nitrogen isotope ratios (&amp;#948;&lt;sup&gt;15&lt;/sup&gt;N) of total nitrogen (TN) were studied for fine aerosol particles (PM&lt;sub&gt;1&lt;/sub&gt;) collected with a 24-h time resolution every two days at a Central European rural background site from September 27, 2013, to August 9, 2014 (n=146).&lt;br&gt;We observed a seasonal cycle of enrichment and depletion of &lt;sup&gt;15&lt;/sup&gt;N in aerosol particles with lower values in winter and higher values in summer. The majority of the yearly data showed a strong correlation between &amp;#948;&lt;sup&gt;15&lt;/sup&gt;N and ambient temperature, supporting an enrichment of &lt;sup&gt;15&lt;/sup&gt;N via isotopic equilibrium exchange between the gas and particulate phases. This process seemed to be one of the main mechanisms for &lt;sup&gt;15&lt;/sup&gt;N enrichment at the Ko&amp;#353;etice site, especially during spring. The most &lt;sup&gt;15&lt;/sup&gt;N-enriched summer and most &lt;sup&gt;15&lt;/sup&gt;N-depleted winter samples were limited by the partitioning of nitrate in aerosols and suppressed equilibrium exchange between gaseous NH&lt;sub&gt;3&lt;/sub&gt; and aerosol NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;. During winter, we observed an event with the lowest &amp;#948;&lt;sup&gt;15&lt;/sup&gt;N values which deviate from temperature dependence. The winter event was connected with prevailing southeast winds and the lowest &amp;#948;&lt;sup&gt;15&lt;/sup&gt;N values were probably associated with agriculture emissions of NH&lt;sub&gt;3&lt;/sub&gt; under low-temperature conditions (&lt;0&amp;#176;C).&lt;br&gt;&lt;br&gt;Acknowledgement:&lt;br&gt;This conference contribution was supported by the Ministry of Education, Youth and Sports of the Czech Republic under the project No. LM2018122, by the ERDF project &quot;ACTRIS-CZ RI&quot; (No. CZ.02.1.01/0.0/0.0/16_013/0001315) and by the Japan Society for the Promotion of Science (JSPS) through Grant-in-Aid No. 24221001. We appreciate the financial support of JSPS fellowship to P. Vodi&amp;#269;ka (P16760) in Japan.&lt;br&gt;&lt;br&gt;Reference:&lt;br&gt;Vodi&amp;#269;ka, P., Kawamura, K., Schwarz, J., Kunwar, B. and &amp;#381;d&amp;#237;mal, V.: Seasonal study of stable carbon and nitrogen isotopic composition in fine aerosols at a Central European rural background station, Atmos. Chem. Phys., 19, 3463&amp;#8211;3479, 2019.&lt;/p&gt;

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