Elemental analysis of archaeological hair compared to soil composition

Abstract

During a salvage archaeology project in 2016–2017, several hundred human remains were recovered from the site of the former First Baptist Church of Philadelphia (FBCP) burial ground, also known as LaGrange Place. This case study focused on two individuals, a child (G-009) and an adult female (G-033), recovered with intact hair masses from the FBCP cemetery. Hair samples from both individuals were studied microscopically and chemically using inductively coupled plasma optical emission spectroscopy (ICP-OES) and mass spectrometry (ICP-MS) multi-elemental analyses. ICP-OES analysis focused on the parts per million (ppm) or milligram per liter (mg/L) concentration of 14 elements, including major and trace elements found in hair and soil (calcium [Ca], chromium [Cr], copper [Cu], iron [Fe], potassium [K], magnesium [Mg], manganese [Mn], sodium [Na], nickel [Ni], phosphorus [P], zinc [Zn]) and three heavy metal toxins (arsenic [As], cadmium [Cd], lead [Pb]). Periodic table semiquantitative heatmap analysis via ICP-MS was also conducted. Elemental analysis revealed the G-009 and G-033 hair samples were chemically distinct from each other and from the soil samples collected at the excavation site. The heatmap results suggest that while burial has a significant effect on the mineral content of hair, hair retains elemental distributions unique to the individual even after centuries of direct soil exposure. Therefore, the mineral composition of both the hair and soil in archaeological contexts should be analyzed to provide insight into the types of environmental exposure experienced by individuals ante- and postmortem.