J. Phys. IV France 107 (2003) 87
Pb isotopic signatures of the atmosphere of the São Paulo city, BrazilM. Babinski, C. Aily, I.R. Ruiz and K. Sato
Centro de Pesquisas Geocronologicas, Instituto de Geociências, Universidade de Sao Paulo, Rua do Lago 562, Sao Paulo, SP, CEP 05508-900, Brazil
Lead isotopic compositions of the atmosphere of the São Paulo city, Brazil, were determined from particulate matter (PM 10) collected on teflon filters, and rainwater samples at the São Paulo University for the period between Auguste 1999 and September/2000. The PM 10 207Pb/ 206Pb ratios range from 0.786 to 0.875, and 208Pb/ 206Pb from 1.934 to 2.119, defining an array on the Pb diagram. Lead concentrations range from 3.02 to 254.52 ng/m 3. Rainwater samples displayed the same isotopic ratios measured on PM 10 collected the same day, thus indicating that aerosols are scavenged by rain. Analyses of possible pollutants sources such as gasoline and ethanol, soot from vehicle exhaust pipes, and particulate material from industrial emissions, collected on fiberglass filters, mostly yielded isotopic compositions falling into an interval defined by 84% of the PM 10 samples ( 207Pb/ 206Pb = 0.840-0.870). However, 15% of the PM 10 samples are more radiogenic, indicating a significant, unidentified radiogenic source ( 207Pb/ 206Pb < 0.780), evident mainly in samples collected during weekends and from November/1999 to April/2000. We suggest that most of the anthropogenic Pb found in the São Paulo atmosphere comes from industrial emissions, since the amount of Pb present in vehicular fuels is negligible.
© EDP Sciences 2003