Isotopic source signatures for atmospheric lead: The Southern Hemisphere

Aerosols collected between 1994 and 1999 at more than 70 different sites af fecting the Southern Hemisphere have been measured for their Pb-206/Pb-207, Pb-208/Pb-207 and Pb-206/Pb-204 ratios and Pb concentrations. Lower ratios are found at the southern tips of Africa, Australia and South America prob ably due to the supply of alkyllead from a common supplier such as Associat ed Octel. The ratios increase in a northerly direction probably due to a ch anging market share in alkyllead or an increasing industrial Pb contributio n. The geographical variations in isotopic signatures made it possible to b roadly characterize the different regions that influence the Southern Hemis phere. Brazil and Argentina exhibited Pb-206/Pb-207, Pb-208/Pb-207,nd Pb-20 6/Pb-204 ratios in aerosols of 1.141-1.184, 2.416-2.442 and 17.77-18.57, re spectively. Mexican aerosols had values of 1.188-1.197, 2.452-2.463 and 18. 46-18.73. Aerosols sampled in Chile had low ratios in the South of 1.063-1. 094, 2.337-2.373 and 16.46-17.13 which increased in a northerly direction. Emissions from South Africa were characterized by ratios 1.067-1.090, 2.340 -2.358 and 16.53-16.99. In 1994-1995 Australia and New Zealand had ratios o f 1.060-1.193, 2.324-2.445 and 16.08-18.54. In 1997 however, the range was narrower: 1.072-1.112, 2.342-2.398 and 16.55-17.36, respectively. These iso topic signatures are potentially useful for tracing sources of pollution an d the movement of air-masses on a global scale. Copyright (C) 2000 Elsevier Science Ltd.