Lead isotope analysis studies

Gale, N. and Z. Stos-Gale (2000), Lead isotope analysis applied to provenance studies, in Ciliberto, E. and G. Spoto (eds.), Modern Analytical Methods in Art and Archaeology, Chemical Analysis Series, Vol. 155, Wiley, New York, pp. 503-584. 

Lead isotopic analysis (J, 2, 3, 4, 5) is a relatively new member of this expanding group of complementary methods. Like the others, it has its own peculiarities, advantages, and disadvantages which have been described. Lead isotope studies help to identify possible geographical origins of the ores from which ancient leads were smelted. Even where specific mines cannot be identified, the objects can still be classified as to which could or could not have had a common origin. The method requires only small sample sizes, and the results are independent of the histories of the objects studied. 

A.D. were found in old mines, and sizable slag deposits suggest at least some level of lead exploitation during Roman times (2). By the careful selection of Roman lead artifacts likely to have been manufactured in Carthage, and the use of lead isotope analysis, it may be possible to confirm the use of Tunisian lead ores during the Roman period. In this preliminary study, analysis of 22 curse tablets by electron microprobe analysis (EMPA) and six tablets by thermal ionization mass spectrometry (TIMS) suggest that these artifacts might be used to better understand Roman lead use and trade. 

Carlson, A.K. 1996. Lead isotope analysis of human bone for addressing cultural affinity a case study from Rocky Mountain House, Alberta. Journal of Archaeological Science 23 557-568. 

With LA, MC-ICP-MS isotope ratio measurements can be performed in just a few minutes per sample as compared with the several hours per sample required for TIMS analysis. In addition, LA-MC-ICP-MS can yield spatially resolved isotope ratio characterization. Thus, provenance studies of ceramic paints, glazes, and slips in situ by LA-MC-ICP-MS measurement of lead and/or other isotope ratios are obvious areas for future development. Hints of the potential of this approach are highlighted in a recent study by Huntley [74], which showed that interaction on different spatial scales can be detected via elemental analysis of paste together with lead isotope analysis of glaze paints on Zuni glazed wares. 

As LA-MC-ICP-MS becomes more accessible, provenance studies may begin to combine elemental and isotopic characterization. Some time ago, Stos-Gale [114] suggested that metal provenance studies could be based on combined lead isotope and trace element analyses, and the same kind of combined approach would seem desirable in the case of turquoise as well as other, seldom analyzed materials such as ceramic glazes. Cooper et al. [115] combined trace element and LA-MC-ICP-MS lead isotope analysis of native copper from North America, but found that the lead isotopes were of little use in source discrimination. 

There are a variety of field and laboratory analytical methods for soil lead measurement, depending on the type of analysis and its purposes in a given evaluation. Bulk soil lead measurement refers to measurement of the total lead content of the soil sample. Chemical speciation and micromineralogical studies in the context of human lead exposure variability refer to amounts of specific chemical forms of lead and their geochemical states. These studies are sometimes done in tandem with relative bioavailability testings, i.e., amounts of lead being absorbed under in vivo or in vitro simulation of in vivo conditions (Casteel et al., 2006) with respect to Pb source attribution. Stable isotopic analysis studies deal with the quantitative stratification of lead s stable isotopic composition into the four main stable isotopes lead-204, lead-206, lead-207, and lead-208 (Gulson et al., 1995, 1997). 

Renson, V., Coenaerts, J., Nys, K., Mattielli, N., Astrom, P., and Claeys, P. (2007) Provenance determination of pottery from Hala Sultan Tekke using lead isotopic analysis preliminary results, in Hala Sultan Tekke 12. Tomb 24, Stone Anchors, Faunal Remains and Pottery Provenance, Studies in Mediterranean Archaeology, Vol 45 (12) (eds. P. Astrom and K. Nys), Paul Astroms Forlag, Savedalen, pp. 53-60. 

Trace-element analysis of metals can give indications of the geographic provenance of the material. Both emission spectroscopy (84) and activation analysis (85) have been used for this purpose. Another tool in provenance studies is the measurement of relative abundances of the lead isotopes (86,87). This technique is not restricted to metals, but can be used on any material that contains lead. Finally, for an object cast around a ceramic core, a sample of the core material can be used for thermoluminescence dating. 

Stos-Gale, Z. A. (1989), Lead isotope studies, in Henderson, J. (ed.), Scientific Analysis in Archaeology, Oxford Univ. Committee for Archaeology, Monograph 19, Oxford, UK, pp. 274-301. 

Srinivasan, S. (1999). Lead isotope and trace element analysis in the study of over a hundred South Indian metal icons. Archaeometry 41 91-116. 

Work by Catanzaro et al. in 1968 (6) led to a new analytical procedure permitting the measurement of isotopic ratios to about 0.05% (95% L.E.) this resulted in the availability of three standard reference materials, so that results could be placed on an absolute basis. This procedure, still the most precise and accurate one available, requires about 1 mg of lead for an analysis. A second procedure (7) has been developed which utilizes silica gel as an ionization enhancer. This method permits the measurement of isotopic ratios to about 0.1% (95% L.E.), but it requires only 0.1 /xg of lead per analysis. In addition, the instrumentation and data handling have been vastly improved so that many samples can be studied quickly and conveniently. 

In the 15 years since Pintozzi s study, great improvements have been made in lead isotope studies. In particular, the instruments and techniques have greatly improved. Additionally, the foundation of a standardized archaeometry database (5) has greatly increased the required instrument precision required for acceptable sourcing of artifacts using the ore source data. As interesting as Pintozzi s results are, her method was not as precise as current TIMS analysis. 

The aim of this preliminary study was to repeat one of Pintozzi s analyses, along with five new samples using updated technology and a more comprehensive lead isotope database. Samples were chosen based on the observed patterns of inclusions from the EMPA analysis. Therefore, tablet 90.3-260 and five other tablets from the 22 analyzed by EMPA were then analyzed by TIMS. Beyond... 

The isotope ratios for the six analyzed curse tablets plus the results from Pintozzi s analysis of curse tablet 90.3—260 are summarized in Table III. These results will supersede those of Pintozzi in all future work due to the imprecision of her 206Pb/204Pb ratios. An estimate of her error in this ratio is approximately 0.6% per amu based on her four analysis of the SRM981 standard. This precision is not within the error limits of the current database. This is in no way a criticism of Pintozzi s analytical ability it is just that the instrument and methods used at that time do not meet the requirements of a modem lead isotope study. 

LA-TOF-ICP-MS may be a useful tool for distinguishing different sources of lead found in low-lead, alkaline-based and lead-based glazes from Mesopotamia. Even with the limitations of the present study, lead-isotope ratios determined by TOF-ICP-MS indicate that multiple ore sources were utilized by makers of Islamic lead-glazed pottery. With the further refinements of Dudgeon et al. (this volume), LA-TOF-ICP-MS promises to be a rapid, cost-effective approach to lead-isotope ratio analysis of glazed pottery. 

ICP-MS has also been used to measure trace elements in archaeological native silver artifacts [345] in order to identify their geographical origins. The low detection limits provided by ICP-MS allowed analysis of trace elements on 3 to 15 mg of sample. The passivation of alloy steels using acid solutions has been studied by XPS measurements of the solid in combination of ICP-MS analysis of the passivation solutions [346,347]. When bullets are crushed on impact, striations cannot be used for identification. The percentage of antimony, trace element composition, and lead isotope ratios in bullets was measured for forensic evidence [348]. The lead isotope ratios were found to be the most useful evidence. 

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