A number of physical and chemical models have been built to describe secondary aerosols (SAs) in the atmosphere; however, direct experimental approaches to simultaneously characterizing the chemical structures and physical properties on the single-particle level are lacking. This lack obscures our understanding of SA formation mechanisms and impedes the development on the accurate prediction and control of air pollution. Here we obtained clear core–shell structural information about the aqueous aerosols employing low-voltage transmission electron microscopy–energy dispersive spectroscopy. The prevalent 10–20% surface tension reduction due to organic matter partitioning has been unveiled. Further analysis and modeling show that smaller SAs can yield greater surface tension reduction, while the pronounced surface tension reduction may enlarge the size of SAs by ≤50%. Our work paves the way for an unprecedented comprehensive single-particle study of the global atmospheric SA problem.

中文翻译：

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低压透射电子显微镜测量单个次级气溶胶颗粒的同步结构和表面张力

已经建立了许多物理和化学模型来描述大气中的次级气溶胶。然而，缺乏在单粒子水平上同时表征化学结构和物理性质的直接实验方法。这种缺乏使我们对SA形成机理的理解变得模糊，并阻碍了对空气污染的准确预测和控制的发展。在这里，我们使用低压透射电子显微镜-能量色散光谱学获得了有关水性气溶胶的清晰的核-壳结构信息。已经揭露了由于有机物分配而导致的表面张力普遍下降10–20％。进一步的分析和建模表明，较小的SA可以产生更大的表面张力降低，而明显降低的表面张力可能会使SAs的尺寸扩大≤50％。我们的工作为全球大气SA问题的史无前例的全面单颗粒研究铺平了道路。