The forensic analysis of soil by FTIR with multivariate analysis

Soil has been utilised in criminal investigations for some time because of its prevalence and transferability. It is usually the physical characteristics that are studied, however the research carried out here aims to make use of the chemical profile of soil samples. It is thought that the land type a soil sample comes from can lead to a particular chemical profile being present, which may make it possible to identify which land type a sample of evidential soil may have come from such as woodland or river sites. This would limit the possibilities significantly and so narrow down the scope for comparison. It could also be used to limit the areas required to be searched in certain cases. The ideal scenario would be that there was a general profile found for each land type and a characteristic profile for each land type location that could be used to identify each specific type of soil and its location specifically. The research we are presenting in this work used sieved (2mm) soil samples taken from the top soil layer (about 10cm) that were then analysed using Fourier Transform Infrared (FTIR) spectroscopy. The spectra obtained were used as raw data in Principal Component Analysis (PCA). Results showed that it was possible to discriminate between soil samples with different soil type and different origins and, with some degree of error, between samples with similar soil type and different origins.