Profiling of human burned bones: oxidising versus reducing conditions

M P M Marques,W Kockelmann,T Coutinho,A P Mamede,D Gonçalves,L A E Batista De Carvalho,E Cunha,S F Parker

doi:10.1038/s41598-020-80462-3

Abstract

Complementary optical and neutron-based vibrational spectroscopy techniques (Infrared, Raman and inelastic neutron scattering) were applied to the study of human bones (femur and humerus) burned simultaneously under either aerobic or anaerobic conditions, in a wide range of temperatures (400 to 1000 °C). This is the first INS study of human skeletal remains heated in an oxygen-deprived atmosphere. Clear differences were observed between both types of samples, namely the absence of hydroxyapatite’s OH vibrational bands in bone burned anaerobically (in unsealed containers), coupled to the presence of cyanamide (NCNH2) and portlandite (Ca(OH)2) in these reductive conditions. These results are expected to allow a better understanding of the heat effect on bone´s constituents in distinct environmental settings, thus contributing for an accurate characterisation of both forensic and archaeological human skeletal remains found in distinct scenarios regarding oxygen availability.

Highlights

Complementary optical and neutron-based vibrational spectroscopy techniques (Infrared, Raman and inelastic neutron scattering) were applied to the study of human bones burned simultaneously under either aerobic or anaerobic conditions, in a wide range of temperatures (400 to 1000 °C)
Three different settings were applied for the burning experiments: (i) combustion, in the presence of oxygen (A); (ii) reductive conditions, volatiles being continuously pumped out (Anunsealed); (iii) oxygen-deprived environment, in a sealed chamber (Ansealed) not allowing the release of the volatiles formed during the burning process, which enabled a re-equilibrium to be attained
Complementary vibrational spectroscopic data was measured for human bones burned under different conditions regarding oxygen availability, for a wide temperature range: combustion, yielding hydroxyapatite at the highest temperatures; absence of oxygen, for two distinct underlying processes—producing either graphitic carbon and Ca-phosphates or HAp

Summary

Introduction

Complementary optical and neutron-based vibrational spectroscopy techniques (Infrared, Raman and inelastic neutron scattering) were applied to the study of human bones (femur and humerus) burned simultaneously under either aerobic or anaerobic conditions, in a wide range of temperatures (400 to 1000 °C). In the last two decades vibrational spectroscopy techniques—Fourier transform infrared (FTIR), Raman and more recently inelastic neutron scattering (INS)—have been shown to be useful tools for the identification and characterisation of burned skeletal remains (faunal and human) from both forensic and archaeological scenarios[6,7,20,21,22,23,24] These techniques allow the assessment, with high accuracy and sensitivity, of the diagenesisinduced chemical alterations in bone, those prompted by burning events (essentially under oxidising conditions): loss of organic components (collagen and lipids), carbonate depletion, and phosphate and hydroxyl rearrangements within the bones inorganic framework. INS, in turn, is an extremely useful technique for probing a hydrogenous material such as bone, the intensity of each vibrational transition being expressed, for a given atom, by the dynamic structure factor

Methods

Results

Conclusion