This report describes an evaluation of the Particle Episodic Model (PEM), an urban scale dispersion model which incorporates deposition, gravitational settling and linear transformation processes into the predecessor model, the Texas Episodic Model (TEM-8). A sensitivity analysis of the model was performed, which included the effects of deposition, gravitational settling and receptor grid size. Recommendations are made to improve the performance and flexibility of the model. PEM was applied to a source inventory of the Philadelphia area to provide a preliminary estimate of source apportionment. PEM modeling employed both hypothetical and actual meteorology. Results indicate that area source emissions dominate TSP, SO2 and sulfate concentrations at urban receptors. A large fraction of the inhalable particles may arrive from distant sources. This report also contains an overview of receptor models (RMs) used for the source apportionment of aerosols. Some diagnostic procedures for RMs are evaluated using a synthetic data set. Described are RM trade-offs and protocols and possible hybrid dispersion/receptor models. Issues regarding the inter-comparison of source apportionments from receptor and dispersion models are highlighted with reference to the 1982 Philadelphia study.

"EPA 600-3-84-074." "April 1984"--Cover Includes bibliographical references. "Cooperative agreement number 809229-01." "Project officer, Jack H. Shreffler."