Black Carbon in Soils as an Indicator for Human-Environment Interactions in the Last 190,000 years
Project continued as Project D6
The F3 project focuses on the relation of human population dynamics with fire. Changes in climate, vegetation and land use frequently went along with regional burning events. On the other hand, from a point of time, yet unknown and certainly long before the beginning of the Neolithic age, fire became an important means of human impact on landscapes. Left behind was black carbon (BC) from incomplete combustion. This project aims at utilising the contents and properties of BC as an indicator for past burning conditions. Sequential oxidation procedures followed by mid-infrared spectroscopy, biomarker and isotope analyses will be applied to different chars and field samples in order to elucidate (1) which charring conditions can be deduced from BC characterisation, (2) how old the BC in soils and sediments is, and (3) when and under which climatic, vegetation and land use conditions burning events were most frequent.
The production of black carbon (BC), which is formed during incomplete combustion processes, has accompanied human life ever since the beginning. The majority of this BC has been preserved in soils and sediments up to date; hence, BC is an ideal, though little explored, indicator for the environmental and land use conditions within the considered time frame. The aim of our project is to utilise the continuum of different chemical BC structures as an indicator for past burning conditions. Our approach is based on further methodological developments of mainly the specific BC molecular marker analyses (BPCA, benzenepolycarboxylic acids):
- Sequential oxidation procedures will be applied to samples of controlled burning events in order to relate the concentration pattern of the consecutively released BPCA to the degree of BC condensation. Together with element analysis of the oxidation residues and mid-infrared spectroscopic analyses (MIRS), the results will be statistically evaluated to deduce past burning energies and major vegetation-fuel types from environmental BC analyses.
- The 13C natural abundance tracing within these BPCA provides an additional indicator of the burning conditions and fuel type.
- For dating of different BC remains, the BPCA are isolated using preparative liquid chromatography for compound-specific 14C-AMS analyses.
- The final application of these methods to deep loess profiles, colluvial materials and sediments will then allow us to relate the contents, ages and properties of BC to changes in climate, vegetation and land use.
Together with other projects of this Collaborative Research Centre we thereby expect to contribute significantly to a better understanding of past human-environment interactions at different climatic periods and land use systems.