Preprints
https://doi.org/10.5194/amt-2021-90
https://doi.org/10.5194/amt-2021-90

  29 Apr 2021

29 Apr 2021

Review status: this preprint is currently under review for the journal AMT.

Rapid measurement of RH-dependent aerosol hygroscopic growth using a humidity-controlled fast integrated mobility spectrometer (HFIMS)

Jiaoshi Zhang1, Steven Spielman2, Yang Wang1,3, Guangjie Zheng1, Xianda Gong1, Susanne Hering2, and Jian Wang1 Jiaoshi Zhang et al.
  • 1Center for Aerosol Science and Engineering, Washington University in St. Louis, St. Louis, Missouri, USA
  • 2Aerosol Dynamics Inc, Berkeley, California, USA
  • 3Department of Civil, Architectural and Environmental Engineering, Missouri University of Science and Technology, Rolla, Missouri, USA

Abstract. The ability of aerosol particles to uptake water (hygroscopic growth) is an important determinant of aerosol optical properties and radiative effects. Aerosol hygroscopic growth is traditionally measured by humidified tandem differential mobility analyzers (HTDMA), in which size-selected dry particles are exposed to elevated relative humidity (RH), and the size distribution of humidified particles are subsequently measured using a scanning mobility particle sizer. As a scanning mobility particle sizer can measure only one particle size at a time, HTDMA measurements are time-consuming, and ambient measurements are often limited to a single RH level. Pinterich et al. (2017b) showed that fast measurements of aerosol hygroscopic growth are possible using a humidity-controlled fast integrated mobility spectrometer (HFIMS). In HFIMS, the size distribution of humidified particles is rapidly captured by a water-based fast integrated mobility spectrometer (WFIMS), leading to a factor of ~10 increase in measurement time resolution. In this study we present a prototype HFIMS that extends fast hygroscopic growth measurements to a wide range of atmospherically relevant RH values, allowing for more comprehensive characterizations of aerosol hygroscopic growth. A dual-channel humidifier consisting of two humidity conditioners in parallel is employed such that aerosol RH can be quickly stepped among different RH levels by sampling from alternating conditioners. The measurement sequence is also optimized to minimize the transition time between different particle sizes. The HFIMS is capable of measuring aerosol hygroscopic growth of six particle diameters under five RH levels ranging from 20 % to 85 % (30 separate measurements) every 25 min. The performance of this HFIMS is characterized and validated using laboratory-generated ammonium sulfate aerosol standards. Measurements of ambient aerosols are shown to demonstrate the capability of HFIMS to capture the rapid evolution of aerosol hygroscopic growth, and its dependence on both size and RH.

Jiaoshi Zhang et al.

Status: open (until 24 Jun 2021)

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Jiaoshi Zhang et al.

Jiaoshi Zhang et al.

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Short summary
In this study, we introduce a newly developed instrument, the humidity-controlled fast integrated mobility spectrometer (HFIMS). The HFIMS can measure the distributions of particle hygroscopic growth factors at six diameters from 35 to 265 nm under five RH levels from 20 to 85 % within 25 min. The HFIMS significantly advances our capability to characterize the hygroscopic growth of atmospheric aerosols over a wide range of relative humidifies.