Organic molecular tracers for particulate air pollution sources

Abstract

The contribution of the major urban air pollution sources to regional particulate air quality problems can be diagnosed by using organic molecular marker techniques. Distinctive organic compounds or compound groups that are present in the emissions from some source types but not others are used to quantify the presence of the effluent from different air pollution sources within atmospheric fine particle samples. The tracer compounds are measured in source samples and in atmospheric samples by gas chromatography–mass spectrometry. Some of the most valuable tracers include hopanes and steranes from petroleum use in motor vehicles; phytosterols, lignans, phenolic products from lignins, and diterpenoids from resins in wood smoke; cholesterol in meat charbroiling smoke; high-molecular-weight odd carbon number n-alkanes in the particles shed as leaves rub together in the wind, and iso- and anteiso-alkanes in cigarette smoke. To date it has been demonstrated that the particles from up to nine different source types can be distinguished from each other simultaneously in the southern California atmosphere by this method. In the future, new analytical methods will increase the family of tracer compounds, assist in the identification of markers for additional sources, and speed the chemical analysis process in the laboratory.

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