Tools for thermal-optical analysis

(TOA, also known as OC/EC)


[Description & Examples ] [Download ] [Citation, CopyLeft, Acknowledgements ]

Description & Examples

These tools facilitate the analysis of data from the Sunset thermal-optical analyzer. They are provided for two purposes:

(1) Thermabsgram: Display the formation and loss of absorbing carbon throughout the analysis. This isn't available on the original thermogram. The figure below shows an example: you can tell exactly when the carbon is charring (pyrolyzing). You can also tell that the carbon leaving the filter in the later part of the analysis (under oxygen) is this pyrolytic carbon; it has the same optical properties.


(2) REACTO: Produce estimates of "EC" (elemental carbon, or the part of the carbonaceous aerosol that absorbs the most light) and "OC" (the rest of it) that are consistent with the measured optical and carbon signals.


thermabsgram is fairly simple and robust. REACTO is still finicky; it requires a few assumptions and iteration. Comments and suggestions are welcome-- the more concrete (and accompanied by sample data), the better.

Download tools here

Download, including readme and sample input files

Caveats & Comments

Sunset has changed their output files over the years. I have tried to make the read-in file general, but it has not been tested on every file type. If it doesn't work on your files, send an example file-- or better yet, adjust ReadRawData so it works on your file, too, and send it back.

Citation, CopyLeft, & Acknowledgements

Governing equations are described in "Revisiting thermal-optical analyses of carbonaceous aerosol using a physical model ," P. Boparai, J. Lee, and T. C. Bond. The manuscript has been in press at Aerosol Science and Technology (July 2008).

These programs are written in MatLab and read the raw data files written by the Sunset analyzer. All scripts are distributed under the Creative Commons by-sa (Attribute/Share Alike) license. I realize this is a little weird because Matlab is proprietary. There's a large community using MatLab, and a lot of people using OC/EC, so I hope that this amount of commonality generates some feedback. Plus, MathWorks now added the ability to produce compiled, standalone executables. I'll look into that when I have time (ha).

This work was sponsored by the U.S. EPA under STAR Grant RD-83108501. Thank you!

Last update: 10 August 2008

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