This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Archaeologists use the strontium in human bone to reconstruct diet and migration in ancient populations. Because mammals discriminate against strontium relative to calcium, carnivores show lower bone Sr/Ca ratios than herbivores. Also, the ratio of 87-Sr to 86-Sr in soils varies with the underlying geology; incorporated into the food chain, this local signature becomes embedded in our bones. The Sr isotopic ratio in the bones of individuals who migrate to a different geologic terrain will gradually change as bone remodels. The isotopic ratio of tooth enamel is fixed at an early age and is not altered later in life. Addition of Sr to bone during post-mortem residence in moist soil or sediment compromises application of the Sr/Ca or Sr-isotope techniques. If this post-mortem Sr resides in a different atomic environment than the Sr deposited in vivo, EXAFS and XANES could allow us to distinguish pristine from contaminated, and thus unreliable, samples. Preliminary findings are positive. The location, at the atomic level, of Sr in human bone is not established. Nor are the locations of other trace elements of archaeological and physiological interest such as Pb, Zn, and Ba. We will address this basic issue by EXAFS analysis of appropriate bone material.
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