Abstract

A water-based particle size magnifier (WPSM) was designed and applied to the wet sampling of airborne nanoparticles at the air-liquid interface (ALI). A T-shaped micromixer was employed to supersaturate the water vapor by instantaneous turbulent mixing between a cold aerosol and hot water vapor-laden gas. The nucleation efficiency of the size-selected test particles of sodium chloride (10 to 40 nm) and lithium sulfate (30 to 150 nm) was evaluated by changing the operation parameters of the WPSM. It was found that over 80% of the test particles (>30 nm) successfully grew into droplets larger than 2.3 µm, which is the cutoff diameter of the impactor. The condensational growth of the water droplets was also confirmed experimentally using an optical particle sizer as well as theoretical calculations. To realize stable deposition at the ALI, a cold wall condenser was employed for draining the excess water vapor from the WPSM. As a result of inertial deposition on the water surface, airborne particles were transported from air to the liquid phase through the ALI, and aqueous ions (Li⁺) were successfully detected by ion chromatography (IC). The detection limit of the WPSM-IC system was as low as 0.33 µg m⁻³-air, which corresponded to the 10-minute sampling of 30-nm particles with a number concentration of approximately 10,000 particles mL⁻¹.

Copyright © 2021 American Association for Aerosol Research

摘要

设计了一种水基粒度放大镜 (WPSM)，并将其应用于气液界面 (ALI) 空气中纳米粒子的湿采样。使用 T 形微混合器，通过冷气溶胶和含有热水蒸汽的气体之间的瞬时湍流混合，使水蒸汽过饱和。通过改变 WPSM 的操作参数来评估尺寸选择的氯化钠 (10 至 40 nm) 和硫酸锂 (30 至 150 nm) 测试粒子的成核效率。结果发现，超过 80% 的测试粒子 (>30 nm) 成功地成长为大于 2.3 µm 的液滴，这是撞击器的截止直径。还使用光学粒度仪和理论计算通过实验证实了水滴的凝聚生长。为了在 ALI 实现稳定沉积，冷壁冷凝器用于从 WPSM 中排出多余的水蒸气。由于惯性沉积在水面上，空气中的颗粒通过 ALI 从空气中传输到液相，水离子（Li⁺ ) 被离子色谱法 (IC) 成功检测到。WPSM-IC 系统的检测限低至 0.33 µg m ^-3 -air，这对应于 10 分钟采样 30-nm 颗粒，其数量浓度约为 10,000 mL ^-1。

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