The application of thermal methods for determining chemical composition of carbonaceous aerosols: A review

Abstract

Thermal methods of various forms have been used to quantify carbonaceous materials. Thermal/optical carbon analysis provides measurements of organic and elemental carbon concentrations as well as fractions evolving at specific temperatures in ambient and source aerosols. Detection of thermally desorbed organic compounds with thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) identifies and quantifies over 100 individual organic compounds in particulate matter (PM) samples. The resulting mass spectra contain information that is consistent among, but different between, source emissions even in the absence of association with specific organic compounds. TD-GC/MS is a demonstrated alternative to solvent extraction for many organic compounds and can be applied to samples from existing networks. It is amenable to field-deployable instruments capable of measuring organic aerosol composition in near real-time. In this review, thermal stability of organic compounds is related to chemical structures, providing a basis for understanding thermochemical properties of carbonaceous aerosols. Recent advances in thermal methods applied to determine aerosol chemical compositions are summarized and their potential for uncovering aerosol chemistry are evaluated. Current limitations and future research needs of the thermal methods are included.

Keywords:

• Carbonaceous aerosol
• thermal desorption
• organic carbon
• organic compounds
• organic markers
• carbon speciation

Acknowledgments

This work was supported by the California Regional PM₁₀/PM_2.5 Air Quality Study (CRPAQS) Agency under the management of the California Air Resources Board and by the U.S. EPA under Contract #R-82805701 for the Fresno Supersite. Additional support was provided by the EPA STAR Grant RD-83108601-0 and the Electric Power Research Institute (EPRI) under contract number EP-P19865/C9746.

Notes

^a Melting point was estimated with Gold and Ogle Method (using EPI Suite™ developed by the U.S. Office of Pollution Prevention Toxics and Syracuse Research Corporation [SRC]).

^b Boling point was estimated with Adapted Stein and Brown Method (using EPI Suite™ developed by the U.S. Office of Pollution Prevention Toxics and Syracuse Research Corporation [SRC]).

^c Vapor pressure was estimated with Modified Grain Method (using EPI Suite™ developed by the U.S. Office of Pollution Prevention Toxics and Syracuse Research Corporation [SRC].

^d Boiling point reported at the pressure of 100 mmHg.

^e Boiling point reported at the pressure of 15 mmHg.

^f Vapor pressure reported at the temperature of 18°C.

^a Calculation based on the detection limits of the organic compounds reported in the thermal desorption method.^{[ 103 ]}

^b Including sample pre-treatment and analytical separation.

^a Total analysis time could not be determined because of insufficient experimental details.