A year-round observation of δ13C of dicarboxylic acids and related compounds in fine aerosols: Implications from Central European background site

<p>Data for paper of following abstract:</p> <p>Isotopic analysis of specific compounds in aerosols can be a useful tool when studying atmospheric processes. Here, we present the results of stable carbon isotope ratio (&delta;¹³C) measurements performed on a one-year set (n = 96, Sep. 2013 - Aug. 2014) of dicarboxylic acids and related compounds in PM₁ at a rural Central European background site, Ko&scaron;etice (Czech Republic).</p> <p>The most ¹³C enriched acid was oxalic (C₂, annual average = -16.6&plusmn;5.0&permil;) followed by malonic (C₃, avg. = -19.9&plusmn;6.6&permil;) and succinic (C₄, avg. = -21.3&plusmn;4.6&permil;) acids. Thus, &delta;¹³C values decreased with an increase in carbon numbers. Azelaic acid (C₉, avg. = -27.2&plusmn;3.6&permil;) was found to be the least ¹³C enriched.</p> <p>A comparison of &delta;¹³C of dicarboxylic acids from other background sites, especially in Asia, shows similar values to those from the European site. This comparison also showed that C₂ is more ¹³C enriched at background sites than at urban ones. In general, we did not observe significant seasonal differences in &delta;¹³C values of dicarboxylic acids at the Central European station. We observed statistically significant differences (p value &lt; 0.05) between winter and summer &delta;¹³C values solely for C₄, glyoxylic acid (&omega;C₂), glutaric acid (C₅) and suberic acid (C₈).</p> <p>The only significant correlations between &delta;¹³C of C₂ and &delta;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 in &delta;¹³C values between C₂ and C₄, the two dominant dicarboxylic acids. Therefore, C₄ appears to be the main intermediate precursor of C₂ throughout the whole year.</p>