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Isotope ratio analyses of trace elements are applied to tooth enamel, ostrich eggshell, and other archaeological hard tissues to infer mobility and other aspects of hominin and animal paleoecology. It has been assumed that these highly mineralized tissues are resistant to diagenetic alteration, but this is seldom tested and some studies document diagenetic alteration over brief time spans. Here, we build on existing research on Maximum Threshold Concentrations (MTCs) to develop screening tools for diagenesis that can inform heavy isotopic analyses. The premise of the MTC approach is that archaeological tissues are likely contaminated and unsuitable for isotope ratio analysis when they exceed characteristic modern concentration ranges of trace elements. Furthermore, we propose a new metric called the Maximum Threshold Ratio (MTR) of 85Rb/88Sr or whole element Rb/Sr, which can be measured simultaneously with 87Sr/86Sr during laser ablation (LA) MC-ICP-MS or applied during post hoc screening of specimens. We analyzed 56 enamel samples from modern Kenyan mammals and 34 modern ostrich eggshells from South Africa, Namibia, and the United States by solution ICP-MS, as well as a subset of shells using LA-MC-ICP-MS. Our results indicate that thresholds are consistent across taxa at a single location, but likely vary across locations. Therefore, MTCs and MTRs need to be tissue and locality specific, but not necessarily taxon-specific. Other important differences are observed between the inner and outer surfaces of the eggshells and between LA and solution ICP-MS. This exploratory study provides guidelines for building reference thresholds to screen enamel and eggshell for diagenesis potentially impacting biogenic isotope ratios.
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Linking ammonium nitrate‐aluminum ( AN‐AL ) post‐blast residues to pre‐blast explosive materials using isotope ratio and trace elemental analysis for source attribution
Abstract Forensic science practitioners are often called upon to attribute crimes using trace evidence, such as explosive remnants, with the ultimate goal of associating a crime with a suspect or suspects in order to prevent further attacks. The explosive charge is an attractive component for attribution in crimes involving explosives as there are limited pathways for acquisition. However, there is currently no capability to link an explosive charge to its source via post‐blast trace residues using isotope ratios or trace elements. Here, we sought to determine if pre‐blast attribution signatures are preserved after detonation and can be subsequently recovered and detected. A field study was conducted to recover samples of post‐blast explosives from controlled detonations of ammonium nitrate‐aluminum (AN‐Al), which were then analyzed via isotope ratio mass spectrometry (IRMS) and inductively coupled plasma‐mass spectrometry (ICP‐MS) for quantitation and profiling of isotopes ratio and trace element signatures, respectively. Oxygen and nitrogen isotope ratios from AN‐Al yielded some of the most promising results with considerable overlap within one standard deviation of the reference between the spreads of pre‐ and post‐blast data. Trace element results from AN‐Al support the findings in the isotope ratio data, with 26 elements detected in both pre‐ and post‐blast samples, and several elements including B, Cd, Cr, Ni, Sn, V, and Zn showing considerable overlap. These preliminary results provide a proof‐of‐concept for the development of forensic examinations that can attribute signatures from post‐blast debris to signatures in pre‐blast explosive materials for use in future investigations.
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- Award ID(s):
- 1828492
- PAR ID:
- 10469655
- Publisher / Repository:
- Journal of Forensic Sciences
- Date Published:
- Journal Name:
- Journal of Forensic Sciences
- Volume:
- 68
- Issue:
- 2
- ISSN:
- 0022-1198
- Page Range / eLocation ID:
- 407 to 415
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1111/1556-4029.15190
