The particle size analysis of soils and its use in forensic science--the determination of particle size distributions within the silt and sand fractions.
Methods are described for the determination of the particle size distributions in small soil samples using a Coulter Counter Model ZB for the silt fraction (60μm–2μm) and conventional sieving for the sand fraction (2mm–60μm). An examination of the reproducibility of the methods using duplicate 1·5g samples of eighteen different soils has shown that they are highly reproducible and that the differences between the soils were easily demonstrated both in the silt and sand particle distributions. The methods have also been shown to be reproducible for sample weights as low as 200mg of whole soil.
The use of grain size distribution analysis of sediments and soils in forensic enquiry.
The use of grain size distribution analysis in forensic enquiry was investigated with reference to four forensic case studies which contained the type of sample restraints and limitations often encountered in criminal case work. The problems of the comparison of trace and bulk samples are outlined and the need for multiple sample analysis is highlighted. It was found that the problems of soil analysis, particularly when the soil was recovered from anthropogenic sources, focused on the lack of identification of pre-, syn- and post-forensic event mixing of materials, thus obscuring the recognition of false-negative or false-positive exclusions between samples. It was found that grain size distribution analysis was a useful descriptive tool but it was concluded that if it were to be used in any other manner the derived results should be treated with great caution. The statistical analyses of these data did not improve the quality of the interpretation of the results.
Aromatic Hydrocarbons in Soil
THE study of various soils by gas chromatography has made it possible to identify several aromatic hydrocarbons as well as thiophene in their aqueous extracts. This report describes the identification of benzene, toluene, ethyl-benzene, p/m-xylene, o-xylene and naphthalene in the soil. Four different types of soil, originating from the AO horizon, have been investigated; meadow soil, cultivated soil, forest soil and podsol. Each of these soils contains all the identified substances, but their concentrations which range from 1 to 5 p.p.m. vary from one soil to another.