Pb isotopic signatures of the atmosphere of the Sao Paulo city, Brazil

Lead isotopic compositions of the atmosphere of the Sao Paulo city, Brazil, were determined from particulate matter (PM10) collected on teflon filters, and rainwater samples at the Sao Paulo University for the period between August/1999 and September/2000. The PM10 Pb-207/Pb-206 ratios range from 0.786 to 0.875, and Pb-208/Pb-206 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 PM10 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 PM10 samples (Pb-207/Pb-206 = 0.840-0.870). However, 15% of the PM10 samples are more radiogenic, indicating a significant, unidentified radiogenic source ((207)pb/Pb-206 < 0.780), evident mainly in samples collected during weekends and from November/1999 to April/2000. We suggest that most of the anthropogenic Ph found in the Sao Paulo atmosphere comes from industrial emissions, since the amount of Ph present in vehicular fuels is negligible.