| NSF Org: |
EAR Division Of Earth Sciences |
| Recipient: |
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| Initial Amendment Date: | March 22, 2016 |
| Latest Amendment Date: | March 22, 2016 |
| Award Number: | 1560912 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Enriqueta Barrera
EAR Division Of Earth Sciences GEO Directorate for Geosciences |
| Start Date: | May 1, 2016 |
| End Date: | April 30, 2019 (Estimated) |
| Total Intended Award Amount: | $38,494.00 |
| Total Awarded Amount to Date: | $38,494.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
660 S MILL AVENUE STE 204 TEMPE AZ US 85281-3670 (480)965-5479 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
AZ US 85281-6011 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | Geobiology & Low-Temp Geochem |
| Primary Program Source: |
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| Program Reference Code(s): | |
| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.050 |
ABSTRACT
This project will investigate the rate of uptake of trace elements like barium, strontium, lead and the rare-earth elements (selected elements from lanthanum to lutetium) into tooth enamel. This project requires a key analytical technique "Secondary Ion Mass Spectrometry (SIMS)" because the spatial scale of measurement is so small. This research is important for understanding how trace elements are taken up in the human body and their fidelity in distinguishing individuals on timescales ranging from years to millions of years. The work will have implications for paleontology, archeology, toxicology and forensics, including the litigation of fossil theft. This funding will support the research and training of a PhD student. This research will be used to leverage educational opportunities for non-scientists in the Boise region and connect researchers unaware of how all areas of microchemical research can benefit from SIMS, a tool that is most commonly applied to semiconductors.
The central focus of this project is to critically evaluate rates of diffusion of numerous trace elements in natural dental enamel. The research has been formulated to answer three main questions: How do diffusivities (D's) of trace elements in enamel depend on 1) charge vs. ionic radius and partitioning? 2) enamel orientation and enamel type? 3) fossilization state? To address these questions, uptake experiments will be conducted over a range of temperatures (4°, 20° and 37 °C) for a range of ions and ionic radii. D's will be measured in different directions for the two main enamel types in mammals - radial and decussate. Measurements in fossil enamel will be compared with similar measurements we make in modern enamel. The data will be inverted using standard diffusion equations, and natural datasets will be evaluated for their consistency (or not) with diffusion-limited uptake. The results will broadly constrain REE, uranium and alkaline element partition coefficients, which will improve models of diffusion rate and uptake of these geochemically- and toxicologically important elements. All data will be published rapidly in accessible international journals and/or archived in on-line geochemical databases. A PhD student will participate in a SIMS workshop, helping develop a community of SIMS users and present her work on fossils and fossilization to elementary school children and the public through established outreach programs.
PROJECT OUTCOMES REPORT
Disclaimer
This Project Outcomes Report for the General Public is displayed verbatim as submitted by the Principal Investigator (PI) for this award. Any opinions, findings, and conclusions or recommendations expressed in this Report are those of the PI and do not necessarily reflect the views of the National Science Foundation; NSF has not approved or endorsed its content.
The purpose of this grant was to determine trace element diffusion rates in mammal enamel, both modern and fossil. This involved sectioning tooth enamel in different orientations and of different types (e.g. radial vs. decussate), using solutions of moderately different chemistry, and analysis using secondary ion mass spectrometry (SIMS). The “collaborative” nature of the research was that the experiments were carried out at Boise State University and the SIMS analyses conducted at Arizona State University.
Our main result is the discovery that diffusion of trace elements in tooth enamel is extremely slow. Each profile consists of a near-edge profile (slow) and an inner profile (fast). At 23 °C, logD (m2/s) is ~-22 (“slow”) and ~-20.5 (“fast”) for Ba, REE, and U. Sr diffuses approximately 10x faster. At 67 °C, values are ~-20.5 (“slow”) and ~-19 (“fast”) for U and REE. Trace elements in tooth enamel diffuse at least 3 orders of magnitude slower than in bone, and do not depend on enamel type, previous fossilization, cation size, or valence. Such low rates of diffusion imply that trace element alteration would affect 1 mm-thick enamel on time scales of 100ka to several Ma for Sr, or several Ma to tens of Ma for Ba, REE, and U. Trace elements may commonly preserve original biogenic values useful for paleodietary and migratory analysis for Plio-Pleistocene fossils, although interpretation of older fossils altered at higher temperatures might be compromised. Thick hominin enamel should prove unusually resistant to trace element alteration.
Our results will be presented in brief at the Geological Society of America annual meeting in Phoenix, and in detail at the American Geophysical Union annual meeting in San Francisco.
This grant directly supported the focused research and educational activities of 2 PhD students at Boise State University – one female student, and the other the first in his family to graduate college and the first to attend graduate school.
Last Modified: 09/19/2019
Modified by: Richard L Hervig
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