Phenolic compounds are common constituents of atmospheric aerosols. They form by pyrolysis of lignin and by biodegradation of plant material and are commonly found in biomass burning plumes, resuspended soil dust, and in anthropogenic secondary organic aerosols (SOA). In this study, we show that reactions of Fe(III), a major constituent of mineral dust, with several phenolic compounds (guaiacol, catechol, syringol, o- and p-cresol) that are common in atmospheric aerosols, result in the formation of water insoluble light-absorbing compounds and reduced Fe(II). The study was conducted under acidic conditions (pH = 1–2), relevant for areas impacted by biomass burning, anthropogenic emissions, and mineral dust. The reaction products have been characterized using a high-performance liquid chromatography coupled to photodiode array and high-resolution mass spectrometry detectors, UV–visible spectroscopy, X-ray photoelectron spectroscopy, and thermal gravimetric analysis. The major identified chromophores are oligomers of the reaction precursors that efficiently absorb light between 300 and 500 nm. The amounts of oligomers vary significantly between the systems studied. The highest amount was observed for guaiacol and catechol, and the least were detected in the syringol experiments, suggesting that the oligomerization proceeds through carbon–carbon coupling preferred at para- and ortho- positions, coupled to the reduction of Fe(III) to Fe(II). The results suggest that aqueous-phase radical reactions of phenolic compounds may be an efficient source of light-absorbing atmospheric organic compounds (brown carbon) that play important roles in Earth’s radiative forcing on global and regional scales and of quinones that can affect health.

中文翻译：

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酚类化合物与Fe（III）的反应对光吸收性低聚物的表征

酚类化合物是大气气溶胶的常见成分。它们是通过木质素的热解和植物材料的生物降解而形成的，通常在燃烧生物质的烟羽，重悬的土壤粉尘和人为的次级有机气溶胶（SOA）中发现。在这项研究中，我们表明，Fe（III）是矿物粉尘的主要成分，它与大气气溶胶中常见的几种酚类化合物（愈创木酚，邻苯二酚，丁香酚，邻甲酚和对甲酚）发生反应水不溶性吸光化合物和还原的Fe（II）。该研究是在酸性条件下（pH = 1-2）进行的，该条件与受生物质燃烧，人为排放物和矿物粉尘影响的区域有关。反应产物的特征是使用与光电二极管阵列和高分辨率质谱检测器耦合的高效液相色谱，紫外可见光谱，X射线光电子能谱和热重分析。鉴定出的主要生色团是反应前体的低聚物，可有效吸收300至500 nm之间的光。在所研究的系统之间，低聚物的量差异很大。愈创木酚和邻苯二酚的含量最高，而在丁香酚实验中却发现的含量最低，这表明低聚反应是通过对位和邻位上优选的碳-碳偶合进行的，以及将Fe（III）还原为Fe （II）。