Abstract View
Measurements of Aerosol Hygroscopic Growth as a Function of RH Using a Humidity-controlled Fast Integrated Mobility Spectrometer
JIAOSHI ZHANG, Steven Spielman, Yang Wang, Susanne Hering, Jian Wang, Washington University in St. Louis
Abstract Number: 394
Working Group: Instrumentation and Methods
Abstract
A humidity-controlled fast integrated mobility spectrometer (HFIMS) was previously developed for fast measurements of aerosol hygroscopic growth (Pinterich et al., 2017). Compared to traditional Humidified Tandem Differential Mobility Analyzers (HTDMA), the HFIMS significantly accelerates hygroscopicity measurements by taking advantage of the capability of the FIMS to rapidly characterize the size spectrum of humidified particles. However, the fast hygroscopicity measurements are limited to a single RH. In this study, we extend the fast measurements to a wide range of RH, therefore allowing comprehensive characterization of aerosol hygroscopic growth over atmospheric relevant RH range, particle phase transitions (e.g., deliquescence), and the variation of aerosol hygroscopic parameter (kappa) with RH.
A dual-channel humidifier with two humidity conditioners in parallel is implemented to achieve quick stepping of aerosol RH. By alternating between the two aerosol conditioners, the HFIMS provides aerosol hygroscopic growth of 6 particle diameters under 6 RH levels ranging from 30% to 90% every 30 min. A humidigraph of size classified particles from 25% to 85% RH can also be obtained by scanning the RH in 10 min, allowing fast characterizations of the deliquescence and efflorescence of aerosol particles. The performance of this improved HFIMS was characterized and validated using laboratory-generated ammonium sulfate aerosol standards. Ambient aerosols in an St. Louis urban area are characterized using the HFIMS and the results will be presented.