Phase behaviour of mixtures of primary and secondary organic aerosols
Abstract
Atmospheric aerosol particles play an important role for air quality and climate. Primary organic aerosol (POA) and secondary organic aerosol (SOA) make up a significant mass fraction of these particles. While POA is directly emitted into the atmosphere, SOA forms from oxidation of precursor gases, followed by gas-to-particle conversion of the oxidation products with lower volatility. In order to describe SOA formation in atmospheric models, and predict their impact on air quality and climate, knowledge on the phase behaviour of mixtures of POA and SOA is required. For instance, it is often assumed that POA enhances SOA formation by providing organic mass for semi-volatile oxidized organic compounds to partition into. This SOA formation mechanism is not likely valid if POA and SOA form separate phases.
Here, using microscopy, we investigated the relative humidity dependent phase behaviour of particles containing mixtures of proxies of POA and SOA. Commercially available organic molecules were used as proxies for POA and SOA, covering a range of oxygen-to-carbon ratio between 0 and 1.0. We show that phase-separated particles form for the majority of mixtures investigated, and that the phase behaviour strongly depends on the oxygen-to-carbon ratio of the two mixed proxies. This has important implications for the air pollution policies being considered to limit SOA formation in urban environments.- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA218.0013M
- Keywords:
-
- 0317 Chemical kinetic and photochemical properties;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0340 Middle atmosphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0394 Instruments and techniques;
- ATMOSPHERIC COMPOSITION AND STRUCTURE