Chemical and microphysical characterization of ambient aerosols with the aerodyne aerosol mass spectrometer

TLDR

Mass spectrometry enables real‑time aerosol measurement, and the aerosol mass spectrometer (AMS) developed by Aerodyne Research, Inc., particularly the ARI thermal vaporization model, is the most widely used instrument for this purpose. The manuscript aims to discuss the strengths and limitations of AMS measurements and review how they characterize particle properties. The AMS employs an aerodynamic lens inlet, thermal vaporization, and electron‑impact or time‑of‑flight mass spectrometry to provide real‑time, size‑resolved chemical speciation and mass loading of fine aerosols. Laboratory and field studies demonstrate the AMS’s versatility, and recent upgrades such as softer ionization and high‑resolution ToF provide more detailed organic aerosol information.

Abstract

The application of mass spectrometric techniques to the real-time measurement and characterization of aerosols represents a significant advance in the field of atmospheric science. This review focuses on the aerosol mass spectrometer (AMS), an instrument designed and developed at Aerodyne Research, Inc. (ARI) that is the most widely used thermal vaporization AMS. The AMS uses aerodynamic lens inlet technology together with thermal vaporization and electron-impact mass spectrometry to measure the real-time non-refractory (NR) chemical speciation and mass loading as a function of particle size of fine aerosol particles with aerodynamic diameters between approximately 50 and 1,000 nm. The original AMS utilizes a quadrupole mass spectrometer (Q) with electron impact (EI) ionization and produces ensemble average data of particle properties. Later versions employ time-of-flight (ToF) mass spectrometers and can produce full mass spectral data for single particles. This manuscript presents a detailed discussion of the strengths and limitations of the AMS measurement approach and reviews how the measurements are used to characterize particle properties. Results from selected laboratory experiments and field measurement campaigns are also presented to highlight the different applications of this instrument. Recent instrumental developments, such as the incorporation of softer ionization techniques (vacuum ultraviolet (VUV) photo-ionization, Li+ ion, and electron attachment) and high-resolution ToF mass spectrometers, that yield more detailed information about the organic aerosol component are also described.