Abstract Eighty five samples of air particulates collected during the summers of 1975–1977 at three rural and one urban sites in New York State were analyzed for up to 13 elements by instrumental neutron activation analysis. Sixteen samples showed high episodic concentrations of several trace elements and sulfate. SO 4 2−, Cr, Zn, As, Se, Br and Sb were distinctly enriched in these aerosols, relative to their crustal abundances. Sc was used as the reference for the crustal component. Episodic and non-episodic events were statistically indistinguishable if only the means and ranges of elemental concentrations and the enrichment factors were considered. However, correlation matrix and factor analysis showed that while non-episodic cases had inexplicably complex factor loading structures, the structure for episodic cases was simple. Episodic events therefore appear to be better indicators of the sources of non-urban aerosols. Five factors were sufficient to account for 87 % of the total variance in the episodic system. When the dependence of the factors on the set of elements was correlated with the elemental emission patterns of probable sources five sources of the trace elements in these aerosols were identified: distant coal-fired power plants (for SO 4 2−, As. Se), refuse incinerators (for Zn, Sb), iron and steel works (for Cr and possibly Fe, Mn). crustal material (for K, Sc, Mn, Fe) and automotive emissions (for Br).