Project Details Evaluation of published lead isotopic data (1950-2013) for a new standard atomic weight of lead

Project No.:
2011-028-1-200
Start Date:
01 April 2012
End Date:
Division Name:
Inorganic Chemistry Division
Division No.:
200

Objective

The purpose of this project is to evaluate isotopic abundance variations of lead in a range of materials, based on peer-reviewed measurements between 1950 and 2013, to create graphical plots of these data, and to provide CIAAW (the Commission on Isotopic Abundances and Atomic Weights) with information to update the “Table of Standard Atomic Weights”.

Description

In August 2013, task group members will convene in Istanbul, prior to the IUPAC General Assembly, in a face-to-face meeting. Detailed discussions and calculations will be discussed on lead isotope data. Particular attention will be paid to authors’ evaluations of uncertainty, the selection of materials for analysis, and the variability of isotope ratio measurements in lead.

It is anticipated that a new standard atomic weight will be recommended for lead and published in the next “Atomic Weights of the Elements“, which will be prepared for Pure and Applied Chemistry.

 

Progress

August 2015 update – Almost 6000 data entries have been evaluated so far; the compiled data was discussed during the 2015 CIAAW meeting. Based on the results (and those of project 2009-023-1-200, TGC: Wieser), a discussion on how to implement the large variation and time shift of radiogenic isotopes in the consideration of standard atomic weights will be described in a publication.

Sep 2017 update – A rather comprehensive data-set on Pb isotope compositions of “normal terrestrial material” has been built by compilation from over 5000 publications. Materials used for Pb isotope measurements have been classified into different groups according to their chemical-physico properties and geological occurrences. Histograms of Pb isotope distribution for each group has been plotted, and their variation ranges have been assessed. Preliminary SNIF diagrams have been made for 204Pb, 206Pb, 207Pb and 208Pb, respectively.

The “normal terrestrial materials” used in the current data-set do not include Th- U-rich minerals, such zircon, UO3 and ThO2. For this kind of minerals, there is no initial Pb in their crystals where they just formed, and all Pb are products from Th or U decay. In other words, there is no 204Pb in those minerals and all Pb are radiogenic. These materials were not regarded as “normal materials”. Now, the subcommittee has made the decision that this kind of minerals should be included in “normal materials”. Subsequently, the data-set needs to be extended.

Dec 2017 update – Task group members have conducted extensive reviews of the peer-reviewed literature on the isotopic composition of lead. They are now in the process of preparing four graphical plots that display the variation in amount fraction of lead-204, lead-206, lead-207, and lead-208 with atomic weight for selected materials, including isotopic reference materials. They have begun drafting a manuscript for Pure and Applied Chemistry that will contain these four figures. This manuscript is planned for submission in early 2018.

August 2019 update – A technical report has been submitted to PAC and is under revision.

Page last updated: 13 Aug 2019