Assessing source characteristics of PM2.5 in the eastern United States using positive matrix factorization.

Fine aerosol (PM2.5) measurements obtained from the first year of operation of the nationwide network of PM2.5 monitors were studied with the factor analysis technique of positive matrix factorization (PMF). PM2.5 mass concentration data were extracted from the Atmospheric Information Retrieval System (AIRS) database of the U.S. Environmental Protection Agency (EPA). PMF was applied to measurements at more than 350 monitoring locations in the eastern half of the United States. Data consisted of PM2.5 24-hr averaged concentrations measured every third day from April through December 1999. The PMF model suggested six factors representing source influences to the PM2.5 mass concentrations at measurement sites. Factor 5, covering much of the Appalachian states, exhibited significant seasonal behavior.