Since traditional forensic soil comparisons do not examine organic- or water-soluble fractions, the current study used high-performance liquid chromatography (HPLC) and ion chromatography (IC) in assessing the qualitative and quantitative variation in these fractions of soil.
The study found that using HPLC and IC to analyze the often unexamined organic- and water-soluble fractions of soil can improve the distinguishing of soil samples by eliminating some false inclusions. The methods used in this study were able to detect both qualitative and quantitative variations in soil over a relatively small geographic area. Although significant variation over time was found in soil characteristics, samples were consistent over shorter time periods. This demonstration of differing soil characteristics underscores the importance of collecting a representative known sample population when assessing a forensic soil comparison. Soil samples (n=120) were collected over the course of 3 weeks from urban, suburban, and rural locations in and around Lansing, MI. Additional samples from six of these locations (two urban, two suburban, and two rural) were collected once a week for 10 weeks for analysis over time. Nine additional samples, equally spaced over a 1-square-meter grid, were collected from these same six locations for spatial analyses. Qualitative and quantitative analysis of the resulting chromatograms separated the 120 samples into 10 groups by HPLC and 23 groups by IC. 6 figures, 3 tables, and 19 references