Abstract An in situ analytical method was demonstrated to measure the proton concentration ([H+]C-RUV) of an aerosol particle by using colorimetry integrated with a Reflectance UV-Visible spectrometer (C-RUV). Acidic particles comprising ammonium, sulfate, and water were generated in a flow tube under varying humidity and employed to calibrate the method using the inorganic thermodynamic models (i.e., E-AIM and ISORROPIA). The predictive [H+]C-RUV equation derived using strongly acidic compositions was then extended to ammonia-rich aerosols, which were lacking in the database of the thermodynamic models. The predictive [H+]C-RUV equation was also expanded to aerosols composed of sodium, ammonium, and sulfate. [H+]C-RUV generally agrees with both E-AIM predicted [H+] and ISORROPIA predicted [H+] for highly acidic aerosols, or aerosols at high humidity. For ammonia-rich aerosols under low humidity, [H+]C-RUV disagrees with that predicted from inorganic thermodynamic models. C-RUV was feasible for ambient aerosols because colorimetry is specific to aerosol acidity. Most aerosols collected at the University of Florida between 2018 and 2019 were acidic. Sodium ions appeared during the spring and summer, as coastal sea breezes traveled inland. The concentrations of ammonium and nitrate were high in the winter due to the phase partitioning of nitric acid and ammonia gases. The fraction of non-electrolytic dialkyl-organosulfate (diOS) to total sulfate is estimated by comparing the actual particle [H+] measured by C-RUV to the [H+] predicted using the inorganic composition and the inorganic thermodynamic models. The diOS fraction varied from 0% to 60% and was higher in the summer months when [H+] is high. Copyright © 2020 American Association for Aerosol Research

中文翻译：

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使用紫外-可见显微光谱仪进行原位气溶胶酸度测量及其在环境空气中的应用

摘要 展示了一种原位分析方法，通过使用与反射型紫外-可见光谱仪 (C-RUV) 集成的比色法来测量气溶胶颗粒的质子浓度 ([H+]C-RUV)。包含铵、硫酸盐和水的酸性颗粒在不同湿度下在流管中生成，并用于使用无机热力学模型（即 E-AIM 和 ISORROPIA）校准该方法。然后将使用强酸性成分推导出的预测性 [H+]C-RUV 方程扩展到热力学模型数据库中缺乏的富含氨的气溶胶。预测的 [H+]C-RUV 方程也扩展到由钠、铵和硫酸盐组成的气溶胶。[H+]C-RUV 通常与 E-AIM 预测的 [H+] 和 ISORROPIA 预测的 [H+] 一致，对于高酸性气溶胶，或高湿度下的气溶胶。对于低湿度下的富氨气溶胶，[H+]C-RUV 与无机热力学模型预测的结果不一致。C-RUV 对于环境气溶胶是可行的，因为比色法特定于气溶胶酸度。佛罗里达大学在 2018 年至 2019 年期间收集的大多数气溶胶都是酸性的。随着沿海海风向内陆移动，钠离子出现在春季和夏季。由于硝酸和氨气的相分配，冬季铵和硝酸盐的浓度很高。通过将 C-RUV 测量的实际颗粒 [H+] 与使用无机成分和无机热力学模型预测的 [H+] 进行比较，估算非电解二烷基有机硫酸盐 (diOS) 与总硫酸盐的比例。diOS 分数从 0% 到 60% 不等，并且在 [H+] 高的夏季月份更高。版权所有 © 2020 美国气溶胶研究协会