An analysis of the effects of diagenesis on elemental concentrations in human bone utilizing x-ray fluorescence technology
Commingling provides a unique challenge in the identification of human remains. The ability to accurately sort the skeletal elements of two or more individuals is vitally important in mass disasters or in other situations in which the bones of one individual become intermixed with those of another individual. Most methods utilized in reconciling commingling rely on visual observations and pair matching undertaken by the lead anthropologist or principle investigator. As such, these methods rely on the experience and expertise of the person performing the analysis. These subjective methods of reconciling commingling can certainly be useful in these cases. However, developing an objective, statistically-based method of analysis that can be utilized in cases where visual matching may not be possible is of utmost importance. This thesis investigates the use of x-ray fluorescence (XRF) technology as a means of sorting remains and reconciling commingling in cases where the remains have been taphonomically altered. Further, this thesis seeks to address the influence of different depositional environments on the chemical composition of bone. To evaluate this method, XRF analyses were conducted on a sample of 40 individuals from the Valley Medical Center (VMC) pauper cemetery (1871-1937) in Santa Clara County, California, and on 20 individuals from the California State University, Chico (CSU, Chico) donated forensic collection. The 40 individuals from the VMC collection originate from the same depositional environment while the 20 individuals form the CSU, Chico collection originate from different depositional environments. This thesis tests the hypothesis that inter-skeletal differences in x-ray fluorescence chemical elemental signatures will be observed between individual skeletons from the VMC collection. In addition, this thesis also tests the hypothesis that no statistically significant differences in intra-skeletal XRF signatures will be observed within individual skeletons in the VMC collection. If these hypotheses are supported, this would demonstrate that diagenesis did not significantly alter chemical signatures in the skeletal remains, indicating that the method has utility for sorting commingled remains in historic burials. If these hypotheses are not supported, the results would indicate that diagenesis obscured in vivo chemical signatures, negating the use of the method on sorting archaeological human remains. Results suggest that variation in certain chemical elemental ratios between individuals is significantly different while the variation in other chemical elemental ratios within individual burials is not significantly different. This lack of statistical significance within burials allows for skeletal elements to be accurately associated with additional skeletal elements from the same burial. Further, the presence of a significant differences between individuals allows for burials to be accurately isolated from one another, greatly enhancing our ability to reconcile commingling when other methods are unable to do so.