Buried bone mineralization

The properties described above have important consequences for the way in which these skeletal tissues are subsequently preserved, and hence their usefulness or otherwise as recorders of dietary signals. Several points from the discussion above are relevant here. It is useful to ask what are the most important mechanisms or routes for change in buried bones and teeth One could divide these processes into those with simple addition of new non-apatitic material (various minerals such as pyrites, silicates and simple carbonates) in pores and spaces (Hassan and Ortner 1977), and those related to change within the apatite crystals, usually in the form of recrystallization and crystal growth. The first kind of process has severe implications for alteration of bone and dentine, partly because they are porous materials with high surface area initially and because the approximately 20-30% by volume occupied by collagen is subsequently lost by hydrolysis and/or consumption by bacteria and the void filled by new minerals. Enamel is much denser and contains no pores or Haversian canals and there is very, little organic material to lose and replace with extraneous material. Cracks are the only interstices available for deposition of material. 

Archaeological fragments of bones and teeth take up fluorine from the surrounding soil and accumulate it in their mineral phase when they are exposed to a humid environment. Geological time spans are needed for this process to reach equilibrium and for the fluorine distribution to become uniform. In cortical parts of long bone diaphysis, an initially U-shaped fluorine concentration profile can be observed, which decreases from the outer surface and the marrow cavity towards the inner parts of the bone and carries information on the exposure duration of the buried object in its shape. The time dependence of the profile slope is usually described in a simplified way by a diffusion model. The quantitative mathematical evaluation of these profiles may provide information on the exposure duration and the physical condition of the samples. Therefore, several attempts to use fluorine profiling as a dating method have been undertaken [3,39], The distribution of... 

While the inorganic matrix of human bones can survive, it can also be contaminated by the soil in which it was buried. Instrumental neutron activation analysis and X-ray fluorescence can be used to detect levels of contamination. Microscopic studies show that voids in the inorganic matrix can be filled with new mineral deposits that have resulted from diagenesis and contamination. 

For bones that had been buried in contact with the soil, a scanning electron microscope (SEM) (JSM-35) was used to examine the samples. A Kevex X-ray system (Si(Li) detector and associated analytical programs) was used to provide semiquantitative analysis of particles observed with the SEM. This analysis, along with the crystal morphology, were used to identify the minerals in the bone samples. X-ray diffraction with Cu-Ka radiation (Ni filter) provided information on the minerals in the bulk bone samples. Powder patterns were obtained with a Phillips diffractometer. 

The contamination of archaeological bone samples by the soil will affect many of the trace elements. For example, the bones buried in the soil (Table I) contain substantially more Ti, Si, Ba, and V than most of the mummy samples. That the Cr concentrations correlate well with the Si02 content suggests that Cr concentrations can be used as a measure of soil contamination. Hancock et al. found that, when using INAA, the Mn, Al, and V levels seemed to be the most sensitive indicators of soil contamination (16). Whether these same elements will indicate the effects of deposition of mineral phases from solution is not clear. 

Once deposited on bone, plutonium is not released until the bone is physically destroyed. It may become buried under a new layer of mineral or may be taken up by special cells that digest foreign materials. As these cells die, the plutonium accumulates in immobilized deposits of hemosiderin, an insoluble iron storage protein that contains a large core of polymeric iron hydroxides and phosphates. These deposits are located close to the bone surfaces in the reticuloendothelial cells of the bone marrow10). 

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