A STUDY OF ATMOSPHERIC AEROSOLS FROM 5 SITES IN MEXICO-CITY USING PIXE

Atmospheric aerosol samples collected in five sites in the Metropolita n Area of Mexico City were analyzed with proton induced X-ray emission (PIXE). Stacked Filter Units (SFU) of the Davis design were employed to obtain samples of fine aerosols (smaller than 2.5 mu m Mean Aerodyn amic Diameter) on polycarbonate filters. The study was conducted durin g the first half of 1996 (16 weeks, from 31st January to 6th June), ex posing the filters once a week, from 8:00 to 14:00 h. PIXE analyses of the filters using a 2 MeV proton beam produced by the Institute de Fi sica, UNAM, 5.5 MV Van de Graaff accelerator were compared with these carried out using a 2.2 MeV proton beam from the 56 cm isochronous cyc lotron at the Universidad de Chile, showing a good correlation between both laboratories. Analysis of variance of the measured elemental con centrations showed differences in the mean concentrations for several elements at the sampling sites. Comparisons with other studies are als o given. (C) 1998 Elsevier Science B.V.