The analysis of preserved and degraded human skeletal material : understanding relationships between bone and the soil environment

Abstract

The relationship that soil interred human bone has with the burial environment has implications for the survival of the organic and inorganic components, including collagen and DNA. The study of both the Chapel House Farm Medieval cemetery, Poulton, Cheshire, UK, and contemporary skeletal remains from cemeteries from Liverpool, U.K. provides new data into the environmental conditions that human bone encounters in the burial environment that are either conducive to preservation or result in complete dissolution of both the organic and inorganic bone matrix.Medieval bones from Chapel House Farm cemetery were analysed to establish the relationship between the organic and inorganic matrix of preserved human bone, and the interaction these had with their burial environment. The use of FTIR and XRF techniques proved to be effective mechanisms in assessing the relationship between the organic and inorganic molecules extracted from the different types of Medieval bone to assess their preservation. These analytical methods were able to establish the degree of soil component intrusion (movement) into the bone, the collagen content, as well as the condition of the mineral matrix of soil interred Medieval bone to be quantified using 2 mg of bone, reducing the need to destroy precious human bone samples.The results from the study of both the Medieval preserved bones from Poulton and Modern contemporary dissolved human remains from Liverpool U.K., where the remains were known to have fully dissolved within 20-30 years post interment, found that the mobility of ions including: Ca, Fe, Mg, K, and P, out of the bone into the soil, does not happen at a constant or predictable rate, but is linked to the environmental soil conditions and burial dynamics. These include: hydrology, seasonal temperature, pH of the soil, burial depth as well as the initial health and age of the individual. Soil samples from two contemporary Liverpool cemeteries were taken from 14 single graves spanning seven time periods (2000- 1850AD) at four depths (0-110cm), along with control samples. They were subjected to X-ray Fluorescence semi-quantitative analysis. The results for the concentrations of five elements: Fe, Mg, Ca, P and K, were statistically tested for trends associated with interred dissolved human remains. The concentration of these ions remained at a relatively constant level in the top soil (0-50 cm) through time. The results demonstrated a clear negative correlation between the levels of Ca and Mg with time, and depth, as well as a significant difference between these components and the control samples. The levels of Fe and K, demonstrated significant trends through two time periods at 50-110 cm, with peaks during initial decomposition and the war years (70-90 years). P demonstrated peaks at 50 and 150 years post interment at all depths.There was a statistical difference in pH of the Liverpool cemetery soils in 50-110 cm depths, and a general increase in the pH from 5-7 in the cemetery soil with relation to time.The presence of ions including: Ca, Fe, Mg, K, and P, derived from human remains from both the preserved Medieval and dissolved contemporary cemeteries persisted in the soil decades after the initial bone dissolution, making this a potentially new technique to assist in the detection of older forensic and historical soil interred human remains; and in addition provides information on the rate of release through time of chemical elements from decomposing human skeletal material.