Physicochemical changes to surface deposited decomposing bone over different timescales: Investigating the influence of bone fractures and the use of non-destructive analytical techniques

Considerations on the drivers of bone diagenesis have received a lot of attention, yet there is still more to understand, particularly in relation to chemical changes that can occur post-mortem, and the rate at which these occur. The physicochemical composition of bone is altered during the post-depositional period, leading to a more thermodynamically stable crystal lattice, thus increasing the long-term survivability of the bone. Research has shown the potential for soft tissue trauma to affect the decomposition process, but the effect of bone trauma and fractures on diagenesis has not yet been considered. Most bone diagenesis research uses destructive analytical techniques, resulting in the loss of samples and the inability to perform repeat analyses. Presented here is a study investigating changes in the physicochemical composition of disarticulated Sus scrofa ribs, with and without fractures, using non-destructive analytical techniques. The aim was to explore the timescales in which physicochemical changes occur and to investigate the potential influence of bone fractures. Intact (control) or fractured (blunt-force or sharp-force) bone samples were deposited on a grassy surface for up to 240 days. Physicochemical changes to the bone sections were analysed using scanning electron microscopy - energy dispersive spectroscopy and Fourier transform infrared spectroscopy with attenuated total reflectance. It was hypothesised that physicochemical changes could be quantified in < 240 days using these techniques, and that the presence of fractures would affect the observed changes. Statistically significant (p < 0.05) losses in Na, K, and Mg and increases in crystallinity were seen over time, as well as significant changes in carbonate content and a significant loss of proteins. Differences physicochemical composition were observed between the undamaged and fractured samples, and the samples with BFT appeared to be the least affected for many elemental and IR parameters indicating BFT could potentially inhibit physicochemical change. The analysis of Na and K showed potential for PMI estimation, as these changed significantly over time, but as these were influenced by the presence of bone fractures, more research is needed fully understand how different variables can affect physicochemical change in bone, particularly the presence of bone fractures/damage.