Lead stable isotope ratios

But not only is the chemistry within the forami-niferal boundary layer drastically perturbed. Stable isotope ratios are also affected, which bears directly on palaeoceanographic interpretations of stable isotopes in fossil foraminifera. For example, preferential uptake of during symbiont photosynthesis under light conditions leads to enrichment of... 

Other information on the sources and dispersion of anthropogenic lead can be derived from the stable isotope ratios of lead (e.g. ° "Pb/ ° Pb) which vary from one mining source to another because of differing Pb/U and Pb/Th for geological sources of lead. In particular, US leaded gasoline for many years had a ° "Pb/ ° Pb ratio of > 1.20, whereas European... 

The advent of laser ablation MC-ICP-MS technology allows the rapid in situ determination of the stable isotope ratios of heavy metals commonly found in sulfide ore deposits (e.g., Cu, Zn, Fe, Sb, Ag) providing important information on the source, transport, and depositional mechanisms of these metals. Pb, Pb, and Pb are formed as the end product of radioactive decay and the isotopic variability of lead results because the elements from which the isotopes form were not evenly distributed in ore bodies. Hence, the analysis of stable lead isotopes in annually laminated lake-sediments is a useful method to study lead pollution history as the relative contribution of pollution and natural lead in sediment samples can be calculated. The analysis of lead isotopes by SIMS has also been used to identify the geographical origin of bullets. 

The four isotopes, as those of any element, have the same chemical properties. The four are not, however, uniformly distributed in the earth s crust the occurrence of three of them, in minerals and rocks, is associated with the radioactive decay of isotopes of thorium and uranium. In most minerals and rocks the relative amounts (or the isotopic ratios) of the isotopes of lead (often expressed relative to the amount of stable lead-204) are generally within well-known ranges, which are independent of the composition of the mineral or rock they are, however, directly related to the amounts of radioactive thorium and uranium isotope impurities in them. 

Flegal and Stukas [406] described the special sampling and processing techniques necessary for the prevention of lead contamination of seawater samples, prior to stable lead isotopic ratio measurements by thermal ionisation mass spectrometry. Techniques are also required to compensate for the absence of an internal standard and the presence of refractory organic compounds. The precision of the analyses is 0.1 -0.4% and a detection limit of 0.02 ng/kg allows the tracing of lead inputs and biogeochemical cycles. 

Isotope ratio measurements are performed whenever the exact ratio, or abundance, of two or more isotopes of an element must be known. For example, the isotopic ratios of lead are known to vary around the world, so it is possible to determine the source of lead in paint, bullets and petrol by knowing the isotopic abundances of the four lead isotopes 204, 206, 207, 208. Another example is the use of stable isotopes as metabolic tracers, where an animal is both fed and injected with an element having artificially enriched isotopes and the fractional absorption of the element can be accurately determined. 

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