Tracing the transport of anthropogenic lead in the atmosphere and in soils using isotopic ratios

The isotopic composition of lead in aerosols and soils in Israel is used to characterize the sources of anthropogenic lead in the region, to ascertain the isotopic composition of natural, rock-derived lead in specific areas, and to determine rates of anthropogenic lead migration in soils. The isotopic composition of lead currently emitted from cars in Israel (Pb-206/Pb-207 = 1.115 +/- 2) is controlled by alkyl-lead produced in France and Germany. In addition to petrol-lead, two more sources of anthropogenic lead can be detected in sampled aerosols: the first one has low concentrations of lead (similar to 4 ng/m(3)) and Pb-206/Pb-207 similar to 1.157, and is most likely lead, emitted in Turkey, that traveled across the eastern Mediterranean basin; the second type of aerosols contains a mixture of lead emitted in several countries including Turkey, Greece, and Ukraine (Pb-206/Pb-207 value of 1.155-1.160; [Pb] similar to 20-30 ng/m(3)). Anthropogenic lead is more accessible for acid leaching than natural lead, therefore, it is mon labile in the soil. The isotopic composition of lead in the acid-leached fraction of near-road soil profiles records the history of alkyl-lead emission in the country. Based on changes in the isotopic composition of lead with soil depth, it is estimated that anthropogenic lead migrates into the soil at approximately 0.5 cm/y. A soil profile from a relatively remote area is less contaminated by anthropogenic lead and displays a different distribution of lead isotopic values with depth. The isotopic composition of lead suggests that natural lead in soils developed on carbonate bedrock is derived from clays, either from the rock-residue (the clay fraction in the carbonate bedrock), or from airborne clay, but not from lead released from the carbonate fraction in the rock. Copyright (C) 1997 Elsevier Science Ltd.