A novel method of monitoring atmospheric particulates in urban environments, a microspectrophotometric technique is described for the analysis of a set of nine impactor samples of atmospheric dust collected near the surface from an urban environment in El Paso, Texas, U.S.A. The sample from each of the six stages is embedded in a KBr micropellet which is analyzed spectroscopically. The analysis revealed a composition and a transition of composition with respect to particle size that was surprisingly close to that of similarly fractionated samples taken from an isolated mountainous site 120 km to the northeast of El Paso. The composition data illustrated a transition from a silicate and carbonate dominated Junge's giant particle fraction (> 2.0 μm dia.) to an ammonium sulfate dominated large particle fraction (between 0.3 and 2.0 μm dia.). The results of the study demonstrate the value of the method used in the detection and identification of the persistent presence of low concentration atmospheric particulates and suggest its use in monitoring urban environment.