Lead concentrations and isotope ratios in speleothems as proxies for atmospheric metal pollution since the industrial revolution

- Study of atmospheric metals from three Belgian stalagmites
- Reconstruction of Pb pollution deposition over last 250 years
- Maximum Pb concentrations are recorded from 1880 to 1905 AD, from 1945 to 1965 AD, and from 1975 to 1990 AD.
- Pb isotopic composition used to identify the main sources of Pb
- The predominant anthropogenic trace metal sources were coal consumption and metallurgical activities.

Lead concentrations and isotope ratios from two speleothems from the Han-sur-Lesse cave in southern Belgium were measured in order to study the ability of speleothems to act as archives of atmospheric pollution. To address this aim we analyzed trace elemental Al and Pb compositions by LA-ICP-MS and ICP-MS as well as Pb isotopes by MC-ICP-MS. The results help to identify three intervals characterized by particularly high enrichment of Pb: from 1880 to 1905 AD, from 1945 to 1965 AD, and from 1975 to 1990 AD. The speleothem record shows similar changes as the known historical atmospheric pollution level in Belgium. Lead isotope ratios discriminate between Pb sources and confirm that coal and gasoline combustion, combined with regional metallurgical activities, were the predominant Pb pollution sources in the stalagmites during the last 250 years. This study opens possibilities to determine anthropogenic versus natural metal sources in well-dated speleothem archives.