Black Carbon in Soils and Sediments as Indicator for Human Environment Interactions in the last 190,000 years
Changes in climate, vegetation and land use frequently went along with regional burning events. Nevertheless, 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. Methodological focus is laid on
- identifying the fuel sources of charcoals from the analyses of lignin-derived phenols and methylated polycyclic aromatic hydrocarbons (PAH) and
- using the ratio of PAH to benzene polycarboxylic acids (BPCA) as a tracer for distinguishing BC of local burning from BC inputs after long-distance transport. By applying these methods to various environmental archives we will finally decipher
- when and under which climatic, vegetation and land use conditions were burning events most frequent, and
- to which degree the intensity of BC deposition relates to the trajectory of "our way to Europe" and the settlement in the Rhine catchment area.
The production of black carbon (BC) formed during incomplete combustion processes accompanied human life ever since. 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. As project "F3" we successfully developed geochemical proxies that allow assigning the properties of charcoal to fire temperatures and therewith grossly to grass, forest and domestic fires. The exact fire reconstruction requires improvement in identifying fuel sources of ancient charcoals. The analyses of charcoal residues in terrestrial archives nevertheless revealed significant changes in black carbon amount and quality correlating with climatic changes and onsets of cultural epochs, respectively. Yet, these analyses were restricted to single palaeosols and limnic profiles in the Rhine area, with little information on the validity of such correlations for other regions studied in this CRC.
The objectives of project D6 are to improve our methodological approach to i) specify fuel sources in fire residues, and ii) to differentiate between BC deposition from local sources and long-distance transport. Moreover, we would like to continue linking the information on past burning history to palaeoclimate and information on settlement history across iii) the whole D cluster area, and along first trajectories of "our way to Europe", as sampled in the collaborating projects.
To achieve the methodological aims we will extend our information for reconstructing fire conditions by including fuel-specific markers into charcoal analyses, such as lignin-derived phenols, alkylated polycyclic hydrocarbons, and magnetic properties. To disentangle the complex interactions between human activity, palaeoclimate and past burning events we will work with limnic sediments from the Eifel Maars and palaeosoils in the Rhine area as well as selected limnic, marine and terrestrial archives provided by the D-Cluster and the projects A3, B1, B2, B3, C1 and C3.