The nature, distribution and significance of amended and anthropogenic soils on old arable farms and the elemental analysis of black carbonised particles

Abstract

Ever since the development of farming humans have been implicitly linked with the landscape. Influences include the manipulation of natural environments by woodland clearance, field developments and animal husbandry. Development can also be determined by the identification and distribution of soils developed and modified by the addition of organic and inorganic components. Anthropogenic or amended soils have been identified in many forms across north west Europe that retain distinctive physical and chemical indications of historical agrarian and settlement history. This thesis researched the on-site distribution of anthropogenic and amended soils across different landuse areas and identified and quantified a range of black carbonised particles in order to investigate their role in the soils ability to retain high elemental concentrations of manuring and elements associated with domestic activity and industrial processes. Three sites in contrasting environments were chosen for analysis; in Fair Isle, the Netherlands and Ireland on the basis of an excellent agararian and settlement history and previous analysis of anthropogenic soils. The fieldwork results showed extremly deep plaggen soils in the Netherlands but considerably shallower horizons of amended arable soils on Fair Isle and in Ireland contrary to previous analysis. There was however, clear evidence of a reduction in anthropogenic and amended soils with increased distance from the farm centres as a result of less manuring. The soil pH, organic matter, particle size, magnetic susceptibility and bulk elemental analysis results showed unexpected increases in the amended soils of Fair Isle and Ireland and reflected a similar manuring process. In the Netherlands the deep plaggen soils had very low results reflecting modern arable farming. The micromorphology results illustrated distinctive characteristics associated with localised manuring techniques. On Fair Isle and in Ireland the main organic manuring material was peat and burnt peat, whereas in the Netherlands the plaggen soils were predominantly composed of meadowland and heathland turf. At all three sites there was a large number of black carbonised and black amorphous inclusions and point counting and image analysis results showed a decrease with depth and distance from settlement nucleii mirroring the fieldwork observations. The elemental analysis conducted has proved to be an extremly useful tool for the identification of various forms of black carbon and for identifying the provenance of high elemental concentrations. The oxygen:carbon ratios confirmed the origins of organic components used in the development of the amended and anthropogenic soils and the elemental analysis showed that at each site over 80% of visually unidentifiable amorphous black carbon particles were heavily decomposed carbonised inclusions. Overall the elemental concentrations within the black carbonised particles was very low but this reflected the elemental results found in the bulk soils and the inclusions contained higher concentrations of P, Ca, K, Fe and Al and considerably lower concentrations of elements associated with domestic activity or industry Zn, Cu, Ba, Cr, As and Pb.