Evaluating the impact of acetic acid chemical pre-treatment on ‘old’ and cremated bone with the ‘Perio-spot’ technique and ‘Perios-endos’ profiles

The impacts of diagenesis on archaeological and palaeontological bone complicate investigations of in-vivo chemical and isotopic characteristics. Such bone is often pre-treated in an attempt to remove diagenetic alteration prior to trace element or isotopic analyses, although very few standardized approaches exist for evaluating pre-treatment effectiveness. In this pilot study, we characterize the diagenetic alteration and assess the impact of acetic acid chemical pre-treatment on the trace element and structural characteristics of four bones from Belgium, including an Early Medieval cremated bone from Broechem and three representative ‘old’ bones of different ages (ca. 40–130 ka) from the Late Pleistocene sedimentary sequence of Scladina Cave. Each bone was analyzed before and after acetic acid pre-treatment using the ‘Perio-spot’ technique and ‘Perios-endos’ profiles. We measured trace element concentrations with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and micro X-ray fluorescence spectroscopy (μXRF). Structural characteristics were investigated with Raman spectroscopy and Fourier transform infrared spectroscopy (FTIR). Our results indicate that chemical pre-treatment had little to no significant impact on the trace element content of the Early Medieval cremated bone, had the most impact on the youngest bone from Scladina Cave, and had less impact on the trace element content of two older bones from Scladina Cave. This suggests that the effectiveness of acetic acid chemical pre-treatment is greater for bones undergoing early diagenetic processes, has minimal impact on highly crystalline cremated bone, and may preferentially leach in-vivo signatures from bones undergoing later diagenesis. The weights of leachates removed from each bone also correspond well with their hypothetical diagenetic states, indicating that researchers could potentially assess the diagenetic state of bones by weighing the leachates produced during acetic acid pre-treatment. Therefore, our new approach may provide a valuable step toward effectively and consistently differentiating among in- and ex-vivo trace element signatures, and, by proxy, those of their isotopes, in archaeological and palaeontological bone