A receptor model for atmospheric aerosols from a southwestern site in Mexico City

Samples of atmospheric aerosols were taken in a southwestern site in Mexico City, during the Fall of 1993, using a Stacked Filter Unit (SFU). This allowed separation of particles with sizes between 2.5 and 15 μm (coarse, deposited on Nuclepore filters), and smaller than 2.5 μm (fine, deposited on Teflon filters). The samples were analyzed using Proton Induced X-ray Emission (PIXE) for elements with atomic numbers between 13 and 26 (Al to Fe), Proton Elastic Scattering (PESA) for hydrogen in the fine fraction, and X-ray Fluorescence (XRF) for elements heavier than Fe. A receptor model is presented using Principal Components Analysis (PCA) in order to find possible sources of the pollutants. Cluster Analysis for each of the fractions was also performed, to assist PCA in the source identification. The multivariate analyses permitted to identify four major sources in each fraction, with soil as the major contributor in both cases.