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Stable isotopes of lead for source identification
1Harvard Medical School and Marine Biological Laboratory, Woods Hole, Massachusetts 02543, USA.
Journal of Toxicology. Clinical Toxicology
|January 1, 1995
Summary
Lead isotope ratios, unique to mining districts, serve as tracers for geological, environmental, and public health applications. Mass spectrometry precisely measures these ratios, aiding in source identification and tracking lead origins.
Area of Science:
- Geochemistry
- Analytical Chemistry
- Environmental Science
Background:
- Lead (Pb) possesses unique stable isotope variations across different mining districts.
- These isotopic variations have been utilized since 1927, initially for geological applications.
- Recent applications extend to archaeology, environmental studies, bio-kinetics, and public health.
Purpose of the Study:
- To explore the applications of stable lead isotope variations.
- To detail the methodology for determining and expressing these isotopic ratios.
- To highlight the utility of lead isotope analysis as a tracer.
Main Methods:
- Determination of the abundances of four stable lead isotopes using specialized mass spectrometry.
- Utilizing rapid mass scanning cycles or multiple collectors for isotopic analysis.
- Expressing relative abundances as atomic ratios (e.g., 206Pb/204Pb, 206Pb/207Pb, 206Pb/208Pb).
Main Results:
- High precision measurements are achievable (e.g., 0.03% for 206Pb/207Pb).
- The three primary isotopic ratios exhibit strong covariance, dependent on ore formation time.
- This covariance allows lead to be traced as a unique signature, changing only upon mixing with different lead sources.
Conclusions:
- Stable lead isotope ratios provide a powerful tracer for diverse applications.
- The method is most effective when potential lead sources are isotopically distinct and limited in number.
- Covariance of ratios typically restricts analyses to a maximum of two potential sources, facilitating source exclusion.