Development of Plant Wax Biomarker Analysis In Soil for Use In Forensic Investigations.

Plant leaves contain a complex mixture of aliphatic lipid compounds which can differ according to plant species. After death or senescence of the plant these can appear in the organic fraction of the soil and can remain there for many years (Dawson et al, 2004). Such biomarkers include long-chain hydrocarbons, fatty alcohols and fatty acids which can be characterized and quantified by GC or GC-MS analysis (Dove & Mayes, 2006). Work on the development of methods to examine additional biomarkers such as triterpenols, ketones, aldehydes and anthropogenic markers such as polycyclic aromatic hydrocarbons (PAH) is ongoing. Use of these markers when comparing soil samples from a crime scene with soil found on clothing or footwear can be of help to the criminal justice system.

It is necessary to be able to analyze very small samples for forensic work so the miniaturization of the biomarker analyses methods is also being developed. Small (~15mg) soil samples were analyzed and the results compared with conventional analysis of 200mg sample size. Elimination of possible contaminants by redistillation of solvents, and reduction of solvent quantities used, along with the use of small volume glassware, cleaned by heating at 450^oC, has enabled GC and GCMS analysis of very small samples to provide reproducible chromatographic data.

Results will be shown from analyses using 15mg samples to compare peat taken at various depths along a core. Peat bog macrofossil vegetation identification will also be illustrated, which will link to the wax marker analysis of peat core samples, and will help to demonstrate change in vegetation over time, from years to centuries. The possibility of linking vegetation identification within soil samples may also be of use in the search phase of a crime investigation, suggesting likely habitats for priority search.

Acknowledgements: RERAD of the Scottish Government and NERC for funding this research.