# Simultaneously Characterizing the Volatility Distribution and Phase State of Submicron Secondary Organic Aerosols Using a Vocus Vaporization Inlet for Aerosols with a Chemical Ionization Mass Spectrometer

## TL;DR

This study uses a new method to measure the volatility and viscosity of organic aerosols in the atmosphere, helping understand their behavior and climate impact.

## Contribution

A new approach combining VIA and Vocus-CIMS enables simultaneous quantification of aerosol composition, volatility, and phase state.

## Key findings

- β-caryophyllene ozonolysis SOA is more viscous and less volatile than α-pinene SOA.
- The method identifies semivolatile to low-volatility species, including highly oxygenated dimers.
- Volatility distributions and phase state parameters like viscosity are quantified in real time.

## Abstract

Volatility and viscosity are important parameters affecting
the
formation, reaction, and fate of atmospheric organic aerosols. In
this study, a Vaporization Inlet for Aerosol (VIA) coupled with a
Vocus chemical ionization mass spectrometer (Vocus-CIMS) using NH4
+ adduct ionization is employed to simultaneously
detect and quantify the molecular composition and volatility of organic
aerosols through a program-controlled temperature ramp, thereby providing
viscosity information. Volatility calibration was conducted with a
series of reference aerosol particles with different chemical compositions,
covering a vapor pressure range from 10–1 to 10–8 Pa. Secondary organic aerosols (SOA) produced from
the potential aerosol mass reactor were analyzed by the VIA-CIMS.
Chemical species ranging from semivolatile to low-volatility, including
highly oxygenated dimers, were identified. Individual ions from the
collected mass spectra were fitted and grouped by volatility basis
sets to yield the volatility distribution of the SOA, allowing for
the quantification of the glass transition temperatures and viscosities.
Results show that β-caryophyllene ozonolysis SOA has lower volatility
and is more viscous than the α-pinene SOA. This approach enables
the online quantification of SOA particle chemical composition and
volatility distribution, while simultaneously characterizing particle
phase state, such as viscosity and water diffusion time, providing
crucial insights into their chemical processes and climate impacts.