Effect of peak inert-mode temperature on elemental carbon measured using thermal-optical analysis
Abstract
Thermal-optical analysis is a conventional method for classifying carbonaceous aerosols
as organic carbon (OC) and elemental carbon (EC). This article examines the effects
of three different temperature protocols on the measured EC. For analyses of parallel
punches from the same ambient sample, the protocol with the highest peak helium-mode
temperature (870°C) gives the smallest amount of EC, while the protocol with the lowest
peak helium-mode temperature (550°C) gives the largest amount of EC. These differences
are observed when either sample transmission or reflectance is used to define the
OC/EC split. An important issue is the effect of the peak helium-mode temperature
on the relative rate at which different types of carbon with different optical properties
evolve from the filter. Analyses of solvent-extracted samples are used to demonstrate
that high temperatures (870°C) lead to premature EC evolution in the helium-mode.
For samples collected in Pittsburgh, this causes the measured EC to be biased low
because the attenuation coefficient of pyrolyzed carbon is consistently higher than
that of EC. While this problem can be avoided by lowering the peak helium-mode temperature,
analyses of wood smoke dominated ambient samples and levoglucosan-spiked filters indicate
that too low helium-mode peak temperatures (550°C) allow non-light absorbing carbon
to slip into the oxidizing mode of the analysis. If this carbon evolves after the
OC/EC split, it biases the EC measurements high. Given the complexity of ambient aerosols,
there is unlikely to be a single peak helium-mode temperature at which both of these
biases can be avoided. Copyright © American Association for Aerosol Research.
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https://hdl.handle.net/10161/6553Published Version (Please cite this version)
10.1080/02786820600714403Publication Info
Subramanian, Ramachandran; Khlystov, Andrey Y; & Robinson, Allen L (2006). Effect of peak inert-mode temperature on elemental carbon measured using thermal-optical
analysis. Aerosol Science and Technology, 40(10). pp. 763-780. 10.1080/02786820600714403. Retrieved from https://hdl.handle.net/10161/6553.This is constructed from limited available data and may be imprecise. To cite this
article, please review & use the official citation provided by the journal.
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