Analysis of the Greenland ice core covering the period from 3000 to 500 years ago-the Greek, Roman, Medieval and Renaissance times-shows that lead is present at concentrations four times as great as natural values from about 2500 to 1700 years ago (500 B.C. to 300 A.D.). These results show that Greek and Roman lead and silver mining and smelting activities polluted the middle troposphere of the Northern Hemisphere on a hemispheric scale two millennia ago, long before the Industrial Revolution. Cumulative lead fallout to the Greenland Ice Sheet during these eight centuries was as high as 15 percent of that caused by the massive use of lead alkyl additives in gasoline since the 1930s. Pronounced lead pollution is also observed during Medieval and Renaissance times.

The pollution history of the atmosphere of the Northern Hemisphere is recorded in the levels of heavy metal impurities in Greenland ice. The possibility also exists of using natural variations in the abundances of lead isotopes to trace the source of this pollution. Lead isotopes have now been measured in ancient Greenland ice with a lead concentration as low as 0.9 pg/g. The results show a depression in the 206 Pb/ 207 Pb ratio between 600 B.C. and 300 A.D., giving unequivocal evidence of early large-scale atmospheric pollution by this toxic metal. This ratio changes from ∼1.201 in ∼8-kyr-old ice to ∼1.183 about 2 kyr ago. Isotopic systematics point to the mining districts in southwest and southeast Spain as the dominant sources of this lead, giving quantitative evidence of the importance of these mining districts to the Carthaginian and Roman civilizations. Lead with a Rio Tinto-type signature represents ∼70% of the lead found in Greenland ice between ∼150 B.C. and 50 A.D. after correcting for the contribution from rock dust indexed to aluminium concentrations. MethodsSample Preparation. We have measured the isotopic composition and concentration of the lead in 26 sections of a 3029 m long ice core from Summit, Greenland (72°34′ N; 37°37′ W; elevation 3238 m), drilled during 1990-1992 for the † This paper is dedicated to the memory of Professor Clair C. Patterson, geochemist at the California Institute of Technology, whose pioneering work on environmental lead has provided the scientific foundation for this study.