Mutagenic Atmospheric Aerosol Sources Apportioned by Receptor Modeling

Abstract

During the winter of 1985, the U.S. Environmental Protection Agency (EPA) collected air quality data and samples in residential locations in Albuquerque, New Mexico and Raleigh, North Carolina as part of its Integrated Air Cancer Project (IACP). One of the major objectives of these field monitoring studies was to evaluate new sampling, analysis, and receptor modeling procedures and to apportion the fine particle mass and mutagenic activity of the organic fraction of the fine particles to the appropriate sources. Samples were collected in the two cities for 12-h periods beginning at 7:00 a.m. and 7:00 p.m. This schedule was followed to aid in resolving the organic and inorganic chemical species emitted from residential wood burning (normally a nighttime activity) and from mobile source emissions (normally a daytime activity). Samples were analyzed for mutagenicity, organic carbon, carbon-14 (14C) content, and inorganic characterizations. Data from these analyses were merged into a single data base and served as input to a multilinear regression (MLR) model that calculates the relative contribution of wood burning and motor vehicle sources to the extractable particle organic matter and mutagenic activity observed in these two cities. The 14C measurements were used to validate the MLR model. Even though the monitoring sites in these cities were both selected and found to be heavily impacted by residential wood burning (83 and 94% of the organic aerosol mass due to wood burning), a proportionately larger percentage of the mutagenicity of the fine particles was attributed to mobile sources (25 and 37%). At both sites the mutagenic potency of the organics extracted from the fine particles were found to be greater (three to five times) for mobile sources when compared with wood smoke extractable organics.