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Updated: Jul 11, 2026
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Split Point Analysis and Uncertainty Quantification of Thermal-Optical Organic/Elemental Carbon Measurements
Published on: September 7, 2019
The IMPROVE_A temperature protocol for thermal/optical carbon analysis: maintaining consistency with a long-term
Judith C Chow1, John G Watson, L W Antony Chen
1Desert Research Institute, Division of Atmospheric Sciences, Reno, NV 89512, USA. judyc@dri.edu
Journal of the Air & Waste Management Association (1995)
|October 5, 2007
Summary
The IMPROVE_A protocol
Area of Science:
- Atmospheric chemistry and air quality monitoring.
- Particulate matter analysis.
Background:
- The U.S. Interagency Monitoring of PROtected Visual Environments (IMPROVE) network has collected data on thermally derived carbon fractions since 1987.
- Organic carbon (OC) and elemental carbon (EC) are crucial for source apportionment and evaluating filter adsorption.
- Previous hardware limitations affected accurate sample temperature representation.
Purpose of the Study:
- To detail the IMPROVE_A temperature protocol for thermal/optical reflectance (TOR) analysis.
- To explain temperature calibration improvements for historical data.
- To assess the impact of temperature changes and oxygen levels on carbon fraction comparability.
Main Methods:
- Implementation of the IMPROVE_A temperature protocol with specific plateaus for OC and EC fractions in helium and oxygen/helium mixtures.
- Development of a new temperature calibration method for older IMPROVE units.
- Establishment of a method to detect trace oxygen in carrier gas.
Main Results:
- The IMPROVE_A protocol utilizes distinct temperature plateaus for OC and EC thermal fractions.
- New calibration confirms improved sample temperature representation in both new and older hardware.
- Changes in temperature protocol affect thermal fractions but not the OC/EC split by TOR.
- Oxygen levels above 100 ppmv impact thermal fraction comparability but not the OC/EC split.
Conclusions:
- The updated temperature protocol ensures long-term consistency of the IMPROVE carbon database.
- The IMPROVE_TOR method remains robust for OC and EC quantification despite protocol changes.
- Accurate measurement of thermal carbon fractions requires controlled carrier gas purity.
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