Variation of lead isotopic composition and atomic weight in terrestrial materials (IUPAC Technical Report)

Abstract

The isotopic composition and atomic weight of lead are variable in terrestrial materials because its three heaviest stable isotopes are stable end-products of the radioactive decay of uranium (238U to 206Pb; 235U to 207Pb) and thorium (232Th to 208Pb). The lightest stable isotope, 204Pb, is primordial. These variations in isotope ratios and atomic weights provide useful information in many areas of science, including geochronology, archaeology, environmental studies, and forensic science. While elemental lead can serve as an abundant and homogeneous isotopic reference, deviations from the isotope ratios in other lead occurrences limit the accuracy with which a standard atomic weight can be given for lead. In a comprehensive review of several hundred publications and analyses of more than 8000 samples, published isotope data indicate that the lowest reported lead atomic weight of a normal terrestrial materials is 206.1462 ± 0.0028 (k = 2), determined for a growth of the phosphate mineral monazite around a garnet relic from an Archean high-grade metamorphic terrain in north-western Scotland, which contains mostly 206Pb and almost no 204Pb. The highest published lead atomic weight is 207.9351 ± 0.0005 (k = 2) for monazite from a micro-inclusion in a garnet relic, also from a high-grade metamorphic terrain in north-western Scotland, which contains almost pure radiogenic 208Pb. When expressed as an interval, the lead atomic weight is [206.14, 207.94]. It is proposed that a value of 207.2 be adopted for the single lead atomic-weight value for education, commerce, and industry, corresponding to previously published conventional atomic-weight values.

Isotopic ratio analysis of individual sub-micron particles via spICP-TOFMS

“…This molar ratio is consistent with others reported for galena. 62 The density scatter plot in Fig. 2D differs slightly from the Sm isotope ratios shown in Fig.…”

“…2 galena. 62 The density scatter plot in Fig. 2D differs slightly from the Sm isotope ratios shown in Fig.…”

A novel simultaneous isotope dilution strategy as a powerful tool in the two-track certification process of trace metal mass fractions: a case study of mercury, cadmium and lead in soil and sediment materials

“…20 In environmental materials Pb has a variable isotopic composition and atomic weight because its three heaviest isotopes are stable end-products of the radioactive decay of uranium ( 238 U to 206 Pb and 235 U to 207 Pb) and thorium ( 232 Th to 208 Pb), and the lightest – 204 Pb is non-radiogenic. 27,28 Following the recent publication of the IUPAC Technical Report on the variation of the Pb isotopic composition and atomic weight in normal materials 29 and the IUPAC Commission on Isotopic Abundances and Atomic Weights (CIAAW) recommendations, 27 a Pb atomic weight of 207.2 ± 1.1 g mol −1 was used and the isotopic composition was taken from the NIST SRM-981 certificate.…”

The Table of Standard Atomic Weights—An exercise in consensus

“…In the IPTEI, the background color of these element cells is yellow 21 . Currently, 14 elements have their standard atomic weights expressed as intervals as discussed later, and the background color of these element cells is pink 17,21,54 …”