Atmospheric deposition of large-scale lead pollution has occurred for at least 3000 years in Europe. Metal production and smelting were the main sources until the twentieth century when emissions from vehicles using alkyl-leaded petrol became dominant. Analyses of lake-sediment and peat deposits in Sweden and other regions in Europe, as well as ice cores from Greenland, suggest synchronous temporal changes in past pollution deposition. Characteristic features in the atmospheric pollution fallout were caused by: the peak in lead pro duction during the Roman period; the marked Mediaeval increase in mining and metal production; the rapidly increasing use of cars and leaded gasoline after the second world war along with increased industrial emissions until around 1970, which was followed by a major improvement due to environmental legislation. For northern Europe at least, these characteristic changes can be used to determine, with reasonable accuracy, at which levels ad 0, ad 1000–1200 and ad 1970 are situated in lake-sediment deposits. To identify these levels, stable lead isotope analyses (206Pb/207Pb ratios) have proven to be very useful besides concentration determinations. Particularly useful are the isotope analyses in areas, such as Sweden, where the differences in 206Pb/207Pb ratios are large between the natural catchment lead and the pollution lead.

There is great concern for contamination of sensitive ecosystems in high latitudes by long-range transport of heavy metals and other pollutants derived from industrial areas in lower latitudes. Atmospheric pollution of heavy metals has a very long history, and since metals accumulate in the environment, understanding of present-day pollution conditions requires knowledge of past atmospheric deposition. We use analyses of lead concentrations and stable lead isotopes ( 206 Pb/ 207 Pb ratios) of annually laminated sediments from four lakes in northern Sweden (∼65°N) to provide a decadal record of atmospheric lead pollution for the last 3000 years. There is a clear signal in the sediments of airborne pollution from Greek and Roman cultures 2000 years ago, followed by a period of "clean" conditions 400-900 A.D. From 900 A.D. there was a conspicuous, permanent increase in atmospheric lead pollution fallout. The sediments reveal peaks in atmospheric lead pollution at 1200 and 1530 A.D. comparable to present-day levels. These peaks match the history of metal production in Europe. This study indicates that the contemporary atmospheric pollution climate in northern Europe was established in Medieval time, rather than in the Industrial period. Atmospheric lead pollution deposition did not, when seen in a historical perspective, increase as much as usually assumed with the Industrial Revolution (1800 A.D.).

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Knowledge of natural, prepollution concentrations of heavy metals in forest soils and temporal trends of soil pollution are essential for understanding present-day pollution (ecotoxicological assessments) and for establishing realistic goals for reductions of atmospheric pollution deposition (critical loads). Soils not exposed to deposition of atmospheric pollution no longer exist and, for example, present lead (Pb) pollution conditions in northern European soils are a consequence of nearly 4,000 years of atmospheric pollution. We use analyses of Pb concentrations and stable Pb isotopes (206Pb/207Pb ratios) of ombrotrophic peat and forest soils from southern Sweden and a model for Pb cycling in forest soils to derive an estimate for the prepollution concentration of Pb in the mor layer of boreal forest soils and to back-calculate Pb concentrations for the last 5,500 years. While the present-day concentra tions of the mor layer are typically 40−100 μg g-1 (0.25−1.0 g m-2), Pb concentrations of pristine forest mor layers in Sweden were quite low, ≤0.1 μg g-1 (≤1 mg m-2). Large-scale atmospheric pollution from the Greek and Roman cultures (ca. 0 AD) increased Pb concentrations to about 1 μg g-1. Lead (Pb) concentrations increased to about 4 μg g-1 following the increase of metal production and atmospheric pollution in Medieval Europe (ca. 1000 AD).

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