Environmental Monitoring at Nydam, a Waterlogged Site with Weapon Sacrifices from the Danish Iron Age. I: A Comparison of Methods Used and Results from Undisturbed Conditions

Abstract

In situ preservation has become a common practice in the management of archaeological sites during the last decade. With this practice follows the need to have good, reliable methods for monitoring the environmental conditions at the sites.

This paper describes the results from seven years of monitoring at the waterlogged site Nydam in Denmark. Results from a range of different monitoring methods are compared, and the advantages and disadvantages of each method are discussed. Measurements of water level, chemical composition, and redox potential are covered, with comparison of results from dipwells, filter probes and measurements directly in the soil.

The results indicate that, with regard to methods 1) in situ measurements directly in the soil give the most reliable results, 2) analysis of water samples from dipwells and filter probes can give reasonable results except for a few species, 3) purging of dipwells before sampling improves the results when combined with a fast sample handling. With regard to the site 4) the burial environment at Nydam is permanently waterlogged, anoxic, slightly acidic, dominated by iron reduction and with a low concentration of dissolved sulphide, 5) there is a significant spatial and temporal variation of the concentrations of most dissolved species, 6) the redox potential as measured with permanently buried gold electrodes is very stable.

Keywords:

• IN SITU PRESERVATION
• ENVIRONMENTAL MONITORING
• METHODOLOGY
• CHEMISTRY
• REDOX POTENTIAL
• NYDAM