School of Environmental Science and Engineering, Tianjin University, Tianjin 300072, China; BIC-ESAT and SKL-ESPC, College of Environmental Sciences and Engineering, Peking University, Beijing 100871, China.
State Key Laboratory of Organic Geochemistry and Guangdong Key Laboratory of Environmental Protection and Resources Utilization, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
J Environ Sci (China). 2025 Mar;149:200-208. doi: 10.1016/j.jes.2023.10.037. Epub 2023 Nov 4.
The acidity of atmospheric aerosols influences fundamental physicochemical processes that affect climate and human health. We recently developed a novel and facile water-probe-based method for directly measuring of the pH for micrometer-size droplets, providing a promising technique to better understand aerosol acidity in the atmosphere. The complex chemical composition of fine particles in the ambient air, however, poses certain challenges to using a water-probe for pH measurement, including interference from interactions between compositions and the influence of similar compositions on water structure. To explore the universality of our method, it was employed to measure the pH of ammonium, nitrate, carbonate, sulfate, and chloride particles. The pH of particles covering a broad range (0-14) were accurately determined, thereby demonstrating that our method can be generally applied, even to alkaline particles. Furthermore, a standard spectral library was developed by integrating the standard spectra of common hydrated ions extracted through the water-probe. The library can be employed to identify particle composition and overcome the spectral overlap problem resulting from similar effects. Using the spectral library, all ions were identified and their concentrations were determined, in turn allowing successful pH measurement of multicomponent (ammonium-sulfate-nitrate-chloride) particles. Insights into the synergistic effect of Cl, NO, and NH depletion obtained with our approach revealed the interplay between pH and volatile partitioning. Given the ubiquity of component partitioning and pH variation in particles, the water probe may provide a new perspective on the underlying mechanisms of aerosol aging and aerosol-cloud interaction.
大气气溶胶的酸度会影响影响气候和人类健康的基本物理化学过程。我们最近开发了一种新颖而简单的基于水探针的方法，可直接测量微尺寸液滴的 pH 值，为更好地了解大气中的气溶胶酸度提供了一种很有前景的技术。然而，环境空气中细颗粒物的复杂化学成分给使用水探针进行 pH 值测量带来了一定的挑战，包括成分之间相互作用的干扰以及类似成分对水结构的影响。为了探索我们的方法的普遍性，我们将其用于测量铵、硝酸盐、碳酸盐、硫酸盐和氯化物颗粒的 pH 值。准确地测定了涵盖广泛范围（0-14）的颗粒 pH 值，从而证明我们的方法可以普遍应用，即使是碱性颗粒也是如此。此外，通过水探针提取常见水合离子的标准光谱，我们还开发了一个标准光谱库。该库可用于识别颗粒成分并克服由于类似影响而导致的光谱重叠问题。利用光谱库，我们可以识别所有离子并确定它们的浓度，从而成功地测量了多组分（硫酸铵-硝酸盐-氯化物）颗粒的 pH 值。我们通过这种方法获得的 Cl、NO 和 NH 消耗的协同效应的见解揭示了 pH 值与挥发性分配之间的相互作用。鉴于成分分配和颗粒中 pH 值变化的普遍性，水探针可能为气溶胶老化和气溶胶-云相互作用的潜在机制提供新的视角。
