Chemical Elemental Analysis Using Portable X-ray Fluorescence as a Means of Sorting Commingled Human Remains

Anthropological analyses include the examination of individual skeletal elements to estimate the biological profile of an unknown individual (age, sex, stature, and ancestry). Commingled human remains (the remains of multiple individuals mixed together) present a significant challenge to these analyses. Commingled skeletal elements may appear similar in size and color, making visual determinations of which bones belong to a certain person insufficient to ensure accurate sorting. Furthermore, when remains are fragmentary as well as commingled, it is more complicated to re-associate each element with a single individual. Traditional methods of sorting commingled remains include pair matching, osteometrics, taphonomic assessment, and assessing overall bone morphology. DNA is another method used to re-associate fragmentary remains, particularly smaller pieces lacking identifiable characteristics. DNA analysis, however, is destructive and may not be affordable or accessible.

The purpose of this study was to test whether the pXRF can be applied to identify chemical elemental signatures unique to an individual for the purpose of sorting commingled human remains. Studying bones at the elemental level may identify chemical signatures unique to an individual. To evaluate whether chemical elements from bone are distinctive enough to allow bone elements from a single individual to be re-associated, bones from forty known individuals donated to the William M. Bass Donated Skeletal Collection from the University of Tennessee, Knoxville were scanned using the pXRF to characterize their chemical elemental composition. Twenty of the donors decomposed on the ground surface at the Anthropology Research Facility (ARF) at the University of Tennessee, Knoxville and twenty donors decomposed in a burial at ARF. The chemical elements from one individual were assessed and compared to the chemical elements from the other skeletons. Comparisons of chemical and elemental composition and concentration values between individuals who decomposed on the surface with buried individuals is recorded to assess differences in between the two environments. A surface to buried comparison is important to understand whether there can be differences seen at the elemental level as well as evaluating if this method works for buried remains which are subject to different taphonomic influences.