Bog Body - Bog Chemistry

Bog Chemistry

A limited number of bogs have the correct conditions for preservation of mammalian tissue. Most of these are located in the colder climes of northern Europe near bodies of salt water. For example, in the area of Denmark where the Haraldskær Woman was recovered, salt air from the North Sea blows across the Jutland wetlands and provides an ideal environment for the growth of peat. As new peat replaces the old peat, the older material underneath rots and releases humic acid, also known as bog acid. The bog acids, with pH levels similar to vinegar, conserve the human bodies in the same way as fruit is preserved by pickling. In addition, peat bogs form in areas lacking drainage and hence are characterized by almost completely anaerobic conditions. This environment, highly acidic and devoid of oxygen, denies the prevalent subsurface aerobic organisms any opportunity to initiate decomposition. Researchers discovered that conservation also required the body to be placed in the bog during the winter or early spring when the water temperature is cold—i.e., less than 4 °C (40 °F). This allows the bog acids to saturate the tissues before decay can begin. Bacteria are unable to grow rapidly enough for decomposition at temperatures under 4 °C.

The bog chemistry environment involves a completely saturated acidic environment, where considerable concentrations of organic acids and aldehydes are present. Layers of sphagnum and peat assist in preserving the cadavers by enveloping the tissue in a cold immobilizing matrix, impeding water circulation and any oxygenation. An additional feature of anaerobic preservation by acidic bogs is the ability to conserve hair, clothing and leather items. Modern experimenters have been able to mimic bog conditions in the laboratory and successfully demonstrate the preservation process, albeit over shorter time frames than the 2,500 years that Haraldskær Woman's body has survived. Most of the bog bodies discovered had some aspects of decay or else were not properly conserved. When such specimens are exposed to the normal atmosphere, they may rapidly begin to decompose. As a result, many specimens have been effectively destroyed, such as the first bog body from Husbäke. It is estimated that 53 bog bodies (the Cashel Man being the latest discovered) have survived.