Sustainability and archaeological heritage. The deterioration of botanical (macro)remains with regard to the physical protection of archaeological sites and landscapes in the Netherlands.
All over Europe there is discussion concerning the degradation of the archaeological record with subsequent loss of archaeological information. This discussion has to lead to a uniform approach to preserve our archaeological heritage in situ, because the heritage is neither regenerable nor replaceable. Despite the regulations provided by the Malta convention, we are still far from such a uniform approach. This is due to differences in policies regarding the management of our archaeological resources in the participating countries, while legislation and planning policies differ from country to country. Furthermore, basic knowledge needed for the physical protection of sites and landscapes is scarce and needs to be developed.
Botanical remains
This study concentrates on botanical materials, which is an important component of many sites. For these materials to survive in the soil, a defined range of conditions must be fulfilled. The main variables are the presence or absence of oxygen, pH, buffer capacity of the soil, and last but not least the microbial populations present. It is evident, however, that most variables influencing the archaeological preservation potential of a soil are closely related to the presence or absence of groundwater.
Preservation assessment
Complementary to other studies, this study concentrates on the preservation of botanical remains in a number of selected areas in the Netherlands. The main objective is to develop an assessment system for the preservation potential of soils in wetland areas, which make up about half of the Dutch territory. Within this objective the following goals were defined:
- to understand the processes of deterioration of botanical materials under various soil conditions;
- to contribute to a model that predicts whether the preservation of archaeological resources is threatened by actions in the planning process;
- to define guidelines with regard to mitigation strategies for the in situ preservation of sites;
- to develop techniques and methods to monitor protected sites;
- to contribute to the development of a theoretical basis for sophisticated approaches to recognizing multiple values with regard to the sustainable development of archaeological heritage.
Biomarkers
All vegetation remnants have their own specific chemical characteristics. The materials consists of a mixture of a large number of organic compounds. A (semi-quantitative) fingerprint of the compounds can be obtained by pyrolysis-gas chromatography-mass spectrometry. This technique causes a fragmentation (pyrolysis) of the complex organic molecules.
The fragments are separated by gas chromatography, and identified by mass spectrometry. The method has been very successful in the study of soil organic matter. Decomposition/humification of organic remains causes a large number or primary components to disappear, with different speed. By identification and quantification of components that react strongly upon decomposition, it is possible to derive a decomposition scale. Some organic remains have very specific chemical components, which allow recognition even when macroscopic identification is no longer possible. We call these biomarkers.
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