The Potential Aerosol Mass (PAM) is an Oxidation Flow Reactor (OFR) that provides a highly oxidizing environment that simulates atmospheric oxidation processes on timescales ranging from a day to several days in a few minutes in the laboratory / field. The reactor was designed by Prof. William Brune’s group at Penn State. In addition to being used as a source of secondary organic aerosol (SOA) particles, the PAM reactor is also used to simulate atmospheric processing of soot and other model primary organic aerosols.
SOA is generated via gas-phase OH oxidation of volatile organic compounds (VOCs) and intermediate volatility organic compounds (IVOCs). The PAM reactor is operated under continuous flow conditions, as opposed to environmental chambers that are typically run in batch mode. The OH/HO2 and OH/O3 ratios in the PAM reactor are similar to tropospheric ratios. The amounts of OH, HO2, and O3 are 100 to 10,000 times larger than in the daytime troposphere. Corresponding OH exposures range from about 1 to 10 days of atmospheric oxidation.
There are advantages and disadvantages to using flow tubes (such as the PAM reactor) compared to environmental “smog” chambers.
Advantages:
- Wider range of oxidant exposure time (1–30 days vs. 1 day)
- Shorter experiment duration (minutes vs. hours or days)
Disadvantages:
- High OH concentrations required to simulate atmospherical aging timescales (108 – 1010 vs. 106 – 107 molec cm-3)
- High (parts-per-million) levels of O3 required for OH production
- UV emission spectrum different than troposphere (peak λ = 254 nm vs λ > 300 nm)
Under investigation:
- Magnitude of wall effects/interactions on measurements
Reference: https://sites.google.com/site/pamwiki/
We hoped you enjoyed our webinar “Formation and Oxidative aging of Secondary Organic Aerosols (SOA) using the Potential Aerosol Mass (PAM) oxidation flow reactor” as much as we did! If you weren’t able to make it, catch our replay.