Exploring seasonal variations in &#948;13C of dicarboxylic acids in fine aerosols: Insights from a Central European background site
Authors: Vodička Petr , Kawamura Kimitaka , Schwarz Jaroslav , Ždímal Vladimír 
Published: March 2024

In this study, we present the measurement results of stable carbon isotope ratio (&#948;13C) performed on a one-year aerosol samples (n = 96, 24h time resolution during Sep. 2013 - Aug. 2014) for dicarboxylic acids (hereafter &#8220;diacids&#8221;) and related compounds in PM1 at a rural background site National Atmospheric Observatory Ko&#353;etice (NAOK), Czech Republic, Central Europe. In previous study on the molecular distributions of diacids (Vodi&#269;ka et al., 2023a), we observed a distinct seasonal variation in the composition of diacids in PM1. In winter, approximately 75% of the organic aerosols originated from anthropogenic sources, whereas in summer, over 75% were attributed to biogenic sources. The objective of this study was to investigate whether these differences are reflected in &#948;13C of diacids.In general, we observed higher &#948;13C values for lower carbon molecules (Vodi&#269;ka et al., 2023b). A comparison of &#948;13C values of major diacids (oxalic (C2), succinic (C4), malonic (C3), azelaic (C9)) with those from other background sites, especially in Asia, shows similar values to those from the European site. This comparison also demonstrated that C2 is more enriched with 13C at background sites than at urban ones. In general, we did not observe significant seasonal differences in &#948;13C values of diacids at NAOK. We observed statistically significant differences (p value < 0.05) between winter and summer &#948;13C values solely for C4, glyoxylic (&#969;C2), glutaric (C5) and suberic (C8) acids.The only significant correlations between &#948;13C of C2 and &#948;13C of C3 were found in spring and summer, suggesting that the oxidation of C3 to C2 is significant in these months with a strong contribution from biogenic aerosols. The strongest season-independent annual correlation was observed between C2 and C4, the two dominant dicarboxylic acids. Therefore, C4 appears to be the main intermediate precursor of C2 throughout the whole year.Acknowledgement:This conference contribution was supported by the Ministry of Education, Youth and Sports of the Czech Republic under the project ACTRIS-CZ-LM2023030, by the Czech Science Foundation grant No. 20&#8211;08304J 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&#269;ka (P16760) in Japan.References:Vodi&#269;ka, P., Kawamura, K., Deshmukh, D.K., Pokorn&#225;, P., Schwarz, J., &#381;d&#237;mal, V., 2023a. Anthropogenic and biogenic tracers in fine aerosol based on seasonal distributions of dicarboxylic acids, sugars and related compounds at a rural background site in Central Europe. Atmos. Environ. 299, 119619. doi:10.1016/j.atmosenv.2023.119619Vodi&#269;ka, P., Kawamura, K., Schwarz, J., &#381;d&#237;mal, V., 2023b. A year-round observation of &#948;13C of dicarboxylic acids and related compounds in fine aerosols: Implications from Central European background site. Chemosphere 337. doi:10.1016/j.chemosphere.2023.139393