The pH of atmospheric aerosols is a key characteristic that profoundly influences their impacts on climate change, human health, and ecosystems. Despite widely performed aerosol pH research, determining the pH levels of individual atmospheric aerosol particles has been a challenge. This study presents a novel analytical technique that utilizes surface-enhanced Raman spectroscopy to assess the pH of individual ambient PM_2.5–10 aerosol particles in conjunction with examining their hygroscopic behavior, morphology, and elemental compositions. The results revealed a substantial pH variation among simultaneously collected aerosol particles, ranging from 3.3 to 5.7. This variability is likely related to each particle’s unique reaction and aging states. The extensive particle-to-particle pH variability suggests that atmospheric aerosols present at the same time and location can exhibit diverse reactivities, reaction pathways, phase equilibria, and phase separation properties. This pioneering study paves the way for in-depth investigations into particle-to-particle variability, size dependency, and detailed spatial and temporal variations of aerosol pH, thus deepening our understanding of atmospheric chemistry and its environmental implications.

中文翻译：

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使用基于表面增强拉曼光谱的新型分析方法直接观察环境气溶胶 pH 值中颗粒间的变化

大气气溶胶的 pH 值是一个关键特征，对其对气候变化、人类健康和生态系统的影响产生深远影响。尽管气溶胶 pH 值研究已广泛开展，但确定单个大气气溶胶颗粒的 pH 水平一直是一个挑战。本研究提出了一种新颖的分析技术，利用表面增强拉曼光谱来评估单个环境 PM _2.5-10气溶胶颗粒的 pH 值，同时检查其吸湿行为、形态和元素组成。结果显示，同时收集的气溶胶颗粒之间的 pH 值存在很大差异，范围为 3.3 至 5.7。这种变化可能与每个颗粒的独特反应和老化状态有关。颗粒间 pH 值的广泛变化表明，同一时间和地点存在的大气气溶胶可以表现出不同的反应性、反应途径、相平衡和相分离特性。这项开创性的研究为深入研究颗粒间的变异性、尺寸依赖性以及气溶胶 pH 值的详细空间和时间变化铺平了道路，从而加深了我们对大气化学及其环境影响的理解。