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10.
Characterization of Water-Soluble Organic Carbon in Atmospheric
Particles: Recent Approaches and Methods
Ewa
Dabek-Zlotorzynska and Luyi Ding
Analysis
and Air Quality Division, Environmental Technology Centre, Environment
Canada, 335 River Road, Ottawa, ON K1A OH3, Canada
Carbonaceous
species, organic carbon (OC) and elemental carbon (EC), constitute
a major, sometimes dominant, fraction of fine particulate matter
(PM). Organic carbon represents a large variety of organic compounds.
Hundreds of non- or semi-polar organic compounds have been quantified
using gas chromatography-mass spectrometry (GC-MS), however much
less information is available on the water-soluble organic compounds
(WSOC).
Given
the potential importance of WSOC in understanding atmospheric
processes, their characterization is crucial to the understanding
of many aspects of air quality and health related issues. In addition,
their measurement is necessary for quantifying the relative contribution
of individual water-soluble organic components to the total WSOC
mass and for assessing the need for identifying additional water-soluble
components. However, their molecular composition still remains
poorly known. The major obstacle encountered in the molecular
characterization of WSOC is the huge complexity of this fraction
with hundreds of different compounds.
Over
the past few years several research groups have proposed different
strategies to obtain new information related to the characteristics
of WSOC. Traditionally, the chemical analysis of aerosols organic
compounds is performed using am individual compound approach,
mostly by GC-MS analysis. However, in these methods a substantial
of polar oxygenated organic compounds, the most water soluble
ones, remains unanalysed, and the component speciation approach
normally ends up long lists of individual compounds which together
account only for a few percent of the WSOC composition.
Furthermore,
a more general chemical characterization of WSOC with the purpose
of characterizing of WSOC composition as a whole, through the
elucidation of the type and concentration of functional groups
characterizing the organic mixture was proposed. In brief, various
methodologies based on a combination of fractionation of bulk
WSOC with various analytical techniques were developed.
This
presentation overviews the recent methodologies proposed for the
chemical characterization of WSOC.
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