VIKING UNST PROJECT: FIELD SEASON 2008 - Nabo

within a deposit, such as disposal of refuse, the presence of manure, plant remains and ash,and the preparation of food (Terry et al. 2004; Guttmann et al. 2005; Bethell and Máté1989; 303; Middleton 2004; 53-54). The abundance and stability of this element within thearchaeological record therefore supports its use as an indicator of human activity. However,the fact that so many processes result in an enhancement of phosphate complicates thesignificance of the results, making it difficult to determine what an enhanced phosphatesignal specifically relates to for the site in question (Middleton 2004; 55).In terms of the assessment of the material from Hamar and Underhoull, the relativeconcentrations of both organic and inorganic phosphates will be compared, providing someindication of the source that dominates the phosphorus signal of the samples. The sampleswill be processed using the standard molybdenum blue colorimetry method using 0.1g ofdried and sieved material (Murphy and Riley 1962, in Holliday and Ganter 2007; 309). Apreliminary assessment of the potential of phosphate analysis has been carried out byRobert Legg from the lower room at Hamar (Legg 2007) and has produced some promisingresults. However, the assessment and interpretation of these samples is ongoing.4.6.3 Soil LipidsThe preservation of lipids within archaeological contexts has been frequently demonstratedwithin the literature (Copley et al. 2005; Heron et al. 1991; Bull et al. 1999; Simpson et al.1999; Heron 2001). It has been demonstrated that key lipid biomarkers can be used toidentify the activities that were occurring. Of importance to the assessment of the depositsat Hamar is the identification of lipids associated with manure. The main lipids of interestare 5β-stigmastanol and coprostanol, lipids frequently associated with herbivorous faecalremains. In addition, bile acids have also been shown to persist in archaeological soils, suchas deoxycholic and lithocholic acid, which are indicative of both human and cattle faecalremains (Simpson et al. 1999; 223; Simpson et al. 1998; 742; Heron 2001; 569). Thepresence of these key lipid biomarkers within the samples collected from Hamar wouldindicate the presence of faecal matter within the lower room of House 1. This in turn couldbe used to suggest whether the lower room was used as a byre during its final use.A total of six samples were collected for analysis from the lower room and prepared forassessment using gas chromatography-mass spectrometry (GC-MS). This technique is oneof the most effective methods of separating, detecting and identifying complex mixtures oflipids (Evershed 1993; 359). This work is in its preliminary phases at present, but will becrucial for the understanding of the function of House 1 within its later period of use.4.6.4 pH measurementsThe measurement of pH indicates the relative acidity or alkalinity for a given sample.Human activity on a site can influence the pH level of the local area through the addition ofcertain materials, such as ash, mortar, vegetation etc. In addition to this, the pH of a depositwill affect the preservation of certain types of materials, as well as the stability of certainelements, such as phosphorus within a deposit. pH measurements will therefore add vitalbackground information to the study of these deposits. Samples were processed using aJenway Model 3150 pH meter using 10-15ml of material.62