Testing the Use of Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy for Differentiating Forensic Soil Samples in Kansas

Abstract

This experiment explored the feasibility of using attenuated total reflectance-Fourier transform infrared radiation (ATR-FTIR) as a preliminary method to identify and differentiate forensic soil samples in Lyon County, Kansas. Current methods used by soil scientists such as polarized light microscopy, inductively coupled plasma- mass spectroscopy (ICP-MS), atomic fluorescence spectroscopy, x-ray fluorescence spectroscopy, and scanning electron microscopy- energy dispersive x-ray (SEM-EDX) are time consuming, destructive, costly, and are not available in all forensic laboratories. ATR-FTIR is nondestructive and is commonly used in forensic laboratories for trace evidence analysis. One hundred surface soil samples and one hundred samples obtained 15.24 cm (6 in) below the surface were collected in five diverse locations of the Ross Natural History Reservation (Ross) located in Lyon County, Kansas. A blind study was conducted with twenty-five additional soil samples from either the surface or subsurface from unknown locations of the Ross. All soil samples were dried, homogenized, and analyzed using ATR-FTIR. Visual comparisons of the data displayed a substantial spectral difference between both layers of soil and minimal observable differences for the areas where soils were sampled. The ATR-FTIR OPUS software correctly identified the origin of 92% of the blind samples. Principal component analysis (PCA) was utilized to highlight small variations and identified the origin of 100% of the blind samples. Results from this study demonstrated that ATR-FTIR can be used as a preliminary screening tool in forensic soil analyses and may offer significant advantages over other, more costly, methods.