ID:
18

Name:
Particle Wall Loss 10-23-2018

Instrument:
Scanning Mobility Particle Sizer (#398)

Chamber:
Nizkorodov Chamber

Temperature (°C):
23

Relative humidity (%):
60

Particle composition:

• SOA

Particle measurement size range:
14.3-673.2

Particle generation method:
Indole and ozone were introduced into the chamber and particles formed.

Date of characterization experiment:
2018-10-23

Months since calibration:

Wall loss experiment description:
SOA is produced in the chamber. Decrease in particle concentration was monitored while not collecting from the chamber.

Wall loss rates calculation method:
In the chamber, the mass concentration of particles (PM) is produced with an unknown and time dependent rate, Source(t), and then lost to the walls with the rate Loss(t). We can describe this kinetically as: dPM/dt = source - loss = source-kw*PM, We assumed that the loss rate is approximated by the first order process proportional to PM. This is an approximation because the loss is particle size dependent but this is the best we can do for our experiments. The constant kw must be determined in a separate experiment in which aerosol is initially produced but then the production is shut off by turning off the lamps.n the situation when Source(t) = 0, and the chamber is just sitting unperturbed without any filter collection, make up air addition, etc., the solution to equation (2) with the zero source term is:PM(t) = PM0xe^-kwt. PMstart is the starting concentration of PM where we let aerosol decay due to the wall loss and time = 0 corresponds to this starting point. In summary, you will need:. Determine kw from available experiments in which you did not collect aerosol from the chamber. Using this kw, calculate the correct PM but for the time period before the filter collection begins.

Frequency of particle loss experiments:

Wall loss correction description:
After finding the wall loss rate constant Kw, use it to correct the particle concentration.

Link to supplemental information:

Additional notes:

Characterization data file:
Particle Wall Loss 12-13-2018.csv