Interlaboratory comparison of Receptor Model results for Houston aerosol

In exercises for the Mathematical and Empirical Receptor Models Workshop (Quail Roost II), nine investigators independently applied receptor models to apportion ambient aerosol mass concentrations to components from emission sources in Houston, TX. The receptor model results were based upon ambient aerosol compositional data supplied to investigators that included mass, elemental and ionic species concentrations for consecutive 12-h sampling periods at the University of Houston between 10 and 19 September 1980. Some investigators performed additional analyses by X-ray powder diffraction, scanning electron microscopy with automated image analysis and X-ray energy spectroscopy and light microscopy. In most cases, the fine (0.2–2.5 μm) and coarse (2.5–15 μm) fractions were analyzed separately by the receptor models. The models tested include effective variance type chemical mass balance, weighted ridge regression, multiple linear regression, factor analysis and target transformation factor analysis. The number of source classes determined ranged from 4 (by multiple linear regression) to 23 (by light microscopy). Results are presented and compared in eight general emissions categories.