This study presents a yearlong data set of 28 medium-chain functionalised carboxylic acids (C5 to C10) in atmospheric aerosol particles (PM10) from a German rural measurement station, which is analysed to obtain seasonal trends and evidences for possible sources of these rarely studied compounds. The analysed carboxylic acids were divided into four main groups: (I) functionalised aliphatic monocarboxylic acids, (II) functionalised aromatic monocarboxylic acids, (III) non-functionalised and functionalised aliphatic dicarboxylic acids, and (IV) aromatic dicarboxylic acids. A concentration maximum in summer was observed for aliphatic carboxylic acids, indicating mainly photochemical formation processes. For example, the highest mean summer concentrations were observed for 4-oxopentanoic acid (4.1 ng m−3) in group I and for adipic acid (10.3 ng m−3) in group III. In contrast, a concentration maximum in winter occurred for aromatic carboxylic acids, hinting at anthropogenic sources like residential heating. The highest mean winter concentrations were observed for 4-hydroxybenzoic acid (2.4 ng m−3) in group II and for phthalic acid (5.8 ng m−3) in group IV. For the annual mean concentrations, highest values were found for adipic acid and 4-oxopimelic acids with 7.8 ng m−3 and 6.1 ng m−3, respectively. The concentrations of oxodicarboxylic acids exceeded those of their corresponding unsubstituted form. Accordingly, straight-chain dicarboxylic acids might act as precursor compounds for their respective oxygenated forms. Similarly, unsubstituted monocarboxylic acids are possible precursors for functionalised aliphatic monocarboxylic acids. The present study contributes to the speciation of organic content on a molecular level of atmospheric particles, as well as giving hints for possible sources for these carboxylic acids.

中文翻译：

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在德国农村地区对大气颗粒中功能化中链羧酸进行的为期一年的研究揭示了季节性趋势和可能的来源

本研究提供了来自德国农村测量站的大气气溶胶颗粒 (PM10) 中 28 种中链官能化羧酸 (C5 到 C10) 的为期一年的数据集，对其进行分析以获得季节性趋势和这些鲜为人知的可能来源的证据化合物。所分析的羧酸分为四个主要组：(I) 官能化脂肪族单羧酸，(II) 官能化芳香族单羧酸，(III) 非官能化和官能化脂肪族二羧酸，以及 (IV) 芳香族二羧酸。在夏季观察到脂肪族羧酸的浓度最大值，这表明主要是光化学形成过程。例如，在 I 组中观察到 4-氧代戊酸 (4.1 ng m-3) 和己二酸 (10. 3 ng m−3) 在第 III 组中。相比之下，芳香族羧酸在冬季出现浓度最大值，暗示着住宅供暖等人为来源。在组 II 中观察到 4-羟基苯甲酸 (2.4 ng m-3) 和在组 IV 中邻苯二甲酸 (5.8 ng m-3) 的最高平均冬季浓度。对于年平均浓度，己二酸和 4-氧庚二酸的最高值分别为 7.8 ng m-3 和 6.1 ng m-3。氧代二羧酸的浓度超过了它们相应的未取代形式的浓度。因此，直链二元羧酸可能作为其各自氧化形式的前体化合物。类似地，未取代的单羧酸是官能化脂肪族单羧酸的可能前体。