Water-soluble organic carbon (WSOC), which is closely related to biogenic emissions, is of great importance in the atmosphere for its ubiquitous existence and rich abundance. Levoglucosan, a typical WSOC, is usually considered to be stable and thus used as a tracer of biomass burning. However, we found that levoglucosan can be photo-oxidized on mineral dust, with formic acid, oxalic acid, glyoxylic acid, 2,3-dioxopropanoic acid, dicarbonic acid, performic acid, mesoxalaldehyde, 2-hydroxymalonaldehyde, carbonic formic anhydride, and 1,3-dioxolane-2,4-dione detected as main products. Further, we observed the heterogeneous uptake of NH₃ promoted by the carboxylic acids stemming from the photocatalytic oxidation (PCO) of levoglucosan. The mineral-dust-initiated PCO of levoglucosan and enhanced heterogeneous uptake of NH₃, which are highly influenced by irradiation and moisture conditions, were for the first time revealed. The reaction mechanisms and pathways were studied in detail by diffuse reflection infrared Fourier transform spectroscopy (DRIFTS), high-pressure photon ionization time-of-flight mass spectrometry (HPPI-ToF-MS) and flow reactor systems. Diverse WSOC constituents were studied as well, and the reactivity toward NH₃ is related to the number of hydroxyl groups of the WSOC molecules. This work reveals a new precursor of secondary organic aerosols and provides experimental evidence of the existence of organic ammonium salts in atmospheric particles.

中文翻译：

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水溶性有机碳（WSOC）在矿物粉尘上的光化学氧化和增强的有机铵形成

与生物排放密切相关的水溶性有机碳（WSOC）由于其无处不在的存在和丰富的存在而在大气中具有重要意义。左旋葡聚糖（一种典型的WSOC）通常被认为是稳定的，因此可用作生物质燃烧的示踪剂。然而，我们发现左旋葡聚糖可以在矿物粉尘上被甲酸，草酸，乙醛酸，2,3-二氧代丙酸，二碳酸，过甲酸，中氧醛，2-羟基丙二醛，碳酸甲酸酐和1进行光氧化。检测到3,3-二氧戊环-2,4-二酮为主要产物。此外，我们观察到了NH ₃的异质吸收左旋葡聚糖的光催化氧化（PCO）产生的羧酸促进了这种作用。首次揭示了左旋葡聚糖的矿物粉尘引发的PCO和增加的NH ₃异质吸收，这受到辐射和水分条件的强烈影响。通过扩散反射红外傅里叶变换光谱（DRIFTS），高压光子电离飞行时间质谱（HPPI-ToF-MS）和流动反应器系统详细研究了反应机理和途径。还研究了不同的WSOC成分以及对NH ₃的反应性与WSOC分子的羟基数有关。这项工作揭示了二次有机气溶胶的新前体，并提供了大气颗粒中有机铵盐存在的实验证据。