VEHICLE-RELATED HYDROCARBON SOURCE COMPOSITIONS FROM AMBIENT DATA - THE GRACE-SAFER METHOD

The composition of three volatile hydrocarbon sources (emissions from vehicles in motion, evaporation of whole gasoline, and gasoline headspace vapor) have been derived from 550 ambient, hourly concentration measurements of 37 C2-C-9 volatile organic compounds (VOC). The measurements were made by automated gas chromatograph in Atlanta, GA, during the summertime of 1990. The source compositions were obtained by a novel combination of graphical analysis and multivariate receptor modeling methodologies: GRACE (Graphical Ratio Analysis for Composition Estimates) and SAFER (Source Apportionment by Factors with Explicit Restrictions). For the relatively unreactive hydrocarbon species, the ambient-derived source compositions were in good agreement with direct source measurements made in Atlanta concurrent with the ambient measurements. The prominence of the whole gasoline profile in the ambient data was an unexpected result. The GRACE/SAFER method may provide a cost-effective alternative to the usual direct source measurement of profiles.