Excavating human skeletons is the closest archaeologists can get to the people who lived in the past. Once excavated the bones are often analysed chemically in order to yield as much information as possible. Most archaeometric analyses performed on samples of human skeletal remains have been performed on a single sample from a tooth or a long bone. In this paper we investigate how a suite of elements (Mg, Al, Ca, Mn, Fe, Zn, As, Sr, Ba, Hg and Pb) are distributed in two medieval skeletons excavated at the laymen cemetery at the Franciscan Friary in Svendborg, Denmark. The analyses have been performed using CV-AAS for Hg and ICP-MS for the rest of the elements. We find that in general Hg concentrations are highest in the trabecular tissues and in the abdomen region. Our data also show that the elements Al, Fe and Mn concentrate in the trabecular tissue and on the surfaces of the bones. The two individuals can be clearly distinguished by Principal Component Analysis of all the measured trace elements. Our data support a previously published hypothesis that the elemental ratios Sr/Ca, Ba/Ca and Mg/Ca are indicative of provenance. Aluminium, Fe and Mn can be attributed to various forms of diagenesis, while Hg is not present in sufficiently large amounts in the surrounding soil to allow diagenesis to explain the high Hg values in the trabecular tissue. Instead we propose that Hg must originate from decomposed soft tissue.
It is found that excess As is mainly of diagenetic origin. The results support that Ba and Sr concentrations are effective provenance or dietary indicators. Migrating behavior or changes in diet have been observed in four individuals; non-migratory or non-changing diet in six out of the 10 individuals studied. From the two most mobile (most changing diet) individuals in the study, it is deduced that the fastest turnover is seen in the trabecular tissues of the long bones and the hands and the feet, and that these bone elements have higher turnover rates than centrally placed trabecular bone tissue, such as from the ilium or the spine. Comparing Sr and published bone turnover times, it is concluded that the differences seen in Sr concentrations are not caused by diagenesis, but by changes of diet or provenance. Finally, it is concluded that there can be two viable interpretations of the Pb concentrations, which can either be seen as an indicator for social class or a temporal development of increased Pb exposure over the centuries.
We describe a procedure for ascertaining the extent of diagenesis in archaeological human skeletons through the distribution of Sr, Ba, Cu, Pb, Fe, and Mn in cross-sections of femoral cortical bone. Element mapping is performed through Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Absolute calibrations of element concentrations were obtained using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) on adjacent dissolved bulk bone samples. By comparing a modern individual to five medieval to early modern Danish skeletons, we demonstrate the degree to which concentrations of trace elements are attributable to diagenesis. Invasion from the exterior bone surface into a degraded part of the outer cortical bone is the most frequently occurring diagenetic change. In the archaeological skeletons investigated, diagenetic modification is restricted to, at most, the outer ca. 0.5 mm of bone. In one femur, Haversian channels were filled with diagenetic material, which appears to have entered the bone through a network of cavities largely made up by Haversian and Volkmann's canals.
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