Reconstructing lead isotope exposure histories preserved in the growth layers of walrus teeth using the SHRIMP II ion microprobe
- Geological Survey of Canada, Ottawa, Ontario (Canada)
- Dept. of Fisheries and Oceans, Winnipeg, Manitoba (Canada)
Development of a microprobe technique to determine Pb isotope ratios within the growth layers of mammal teeth could have widespread applications in Pb toxicology, Pb pollution tracing, and human and animal ecology. Here, the SHRIMP II ion microprobe is shown to possess sufficient sensitivity, accuracy, and precision to satisfactorily determine Pb isotope ratios in the canine tooth cementum of a walrus (Odobenus rosmarus rosmarus), with a sampling resolution of 130 {micro}m. The tooth layers were estimated to contain only 1--3 {micro}g/gf Pb. By combining multiple replicates within each annual layer, the {+-}1 SE uncertainty was typically {+-}1% for {sup 206}Pb/{sup 207}Pb and {+-}0.5% for {sup 208}Pb/{sup 207}Pb. Significant isotopic differences were found between layers deposited at age 10 and ages 2, 27, and 30. This result, together with corroborative data on excised cementum fragments analyzed by thermal ionization mass spectrometry, indicates that the animal migrated into different geological terrains several times during its life. There was no evidence of exchange between the Pb deposited in early growth layers and more recent ambient Pb.
- OSTI ID:
- 355508
- Journal Information:
- Environmental Science and Technology, Vol. 33, Issue 10; Other Information: PBD: 15 May 1999
- Country of Publication:
- United States
- Language:
- English
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