DETERMINATION OF ELEMENTAL CONCENTRATIONS IN ATMOSPHERIC AEROSOLS IN MEXICO-CITY USING PROTON-INDUCED X-RAY-EMISSION, PROTON ELASTIC-SCATTERING, AND LASER-ABSORPTION

A study of the concentrations of elements present in atmospheric aeros ols at two different sites in Mexico City was done with samples taken during September 1990 and February 1991. The samples were taken daily during 6 h periods (from 6:00 to 12:00 hr), using a Stacking Filter Un it (SFU) of the Davis design. This allowed the separation of particles with sizes ranging from 2.5 to 15 mu m (coarse mass), and smaller tha n 2.5 mu tm (fine mass). Analyses of the samples with Proton Induced X -ray Emission (PIXE) gave information on elements heavier than Ne, Pro ton Elastic Scattering Analysis (PESA) on hydrogen contents, and the L aser Integrating Plate Method (LIPM) was used on the fine fraction to determine soot contents. Cluster Analysis is applied to the sample set in order to identify the emission sources of the elements. Additional ly, the relationship to several meteorological variables is presented. Comparisons with previous studies are also provided.