Identification, quantification and sourcing of fossil hydrocarbons in ancient Egyptian mummies by V and Ni trace elements†

Egyptian mummies are often covered with black embalming matter, which is made of complex mixtures of natural organic substances such as vegetable resins, beeswax, animal fats, gums, and vegetable oils, as well as bitumen. In this work, we used proton-induced X-ray emission (PIXE) and electron paramagnetic resonance (EPR) to investigate the potential of certain transition metals, in particular V and Ni, as probes for detecting the presence of bitumen and tracing its origin and alteration in this black embalming matter. PIXE analysis showed that all the mummies studied in this work (bird, ram, crocodile, human), which span a period of about 1000 years and come from different sites in Egypt, have a nearly constant Ni/V ratio close to that of bitumen from the Dead Sea, suggesting a well-defined source of bitumen supply. The same conclusion was reached by EPR analysis of vanadyl porphyrins and carbonaceous radicals. The presence of an excess of radicals in the black matter from several mummies indicates that they probably contain some carbonized organic matter in addition to bitumen. This combined PIXE-EPR methodology is quantitative and sensitive since a few % of bitumen can be non-destructively detected in a mummy sample weighing only a few mg. The combination of these two techniques can provide new information on the thermal history (preparation recipes) and redox history (natural degradation) of this black matter.