Sand fraction is not suitable for forensic investigations in subtropical soils

Abstract

How to cite: Melo VF, Testoni SA, Dawson LA, Salvador FAS. Sand fraction is not suitable for forensic investigations in subtropical soils. Rev Bras Cienc Solo. 2020;44:e0190174.

Multimodal spectroscopy with chemometrics for the forensic analysis of the inorganic content of Western Australian sandy soils

“…Within forensic soil science, techniques for the analysis of the inorganic content within samples have been widely established across many disciplines (1,2,4,6,8,9,20). The most common methods currently utilised include polarised light microscopy for general identification of minerals and rocks (1), inductively coupled plasma mass spectrometry (ICP-MS) for semi-quantitative comparisons of the elemental composition (10,21,22), and x-ray diffraction (XRD) or scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) for mineral speciation and characterisation of native metals (7,13,23,24). In many methodologies, several techniques are undertaken on separated fractions of soil, allowing further differentiation compared to the bulk chemistry (10,21,23,24).…”

“…Whilst the use of chemometrics has been extensively applied to organic forensic soil analysis (4,6,8,9,26,27,(32)(33)(34)(35), there has been limited reports of use with inorganic data (5,24,36,37). In 2011, Jantzi and Almirall developed a method for LIBS analysis of surface soil samples, using PCA to discriminate between sample sites (37).…”

“…Kammrath et al then published a case study utilising a novel technique that combined morphologically-directed Raman spectroscopy with PCA to evaluate forensic soil samples (36), while Testoni et al worked towards validation of a standard operating procedure for forensic soil analysis utilising ICP optical spectrometry, thermogravimetry analysis, and XRD alongside PCA (5). More recently, Melo et al investigated the use of particle size distribution, XRD, and SEM-EDX to characterise the sand fraction of subtropical soils, using PCA and Bray-Curtis dissimilarity measures to discriminate between samples (24). This study investigated soil types like the dry, sandy soils found in Western Australia, however their method was unsuitable for effective discrimination between these soils.…”

“…The most common methods currently utilised include polarised light microscopy for general identification of minerals and rocks (1), inductively coupled plasma mass spectrometry (ICP-MS) for semi-quantitative comparisons of the elemental composition (10,21,22), and x-ray diffraction (XRD) or scanning electron microscopy with energy dispersive x-ray spectroscopy (SEM-EDX) for mineral speciation and characterisation of native metals (7,13,23,24). In many methodologies, several techniques are undertaken on separated fractions of soil, allowing further differentiation compared to the bulk chemistry (10,21,23,24). The comparison of the quartz-recovered fine fraction (primary and secondary minerals < 20 mm found as coatings on quartz grains) is a method recently developed by Pitts and Clarke, which allows for differentiation of minute and fractionated forensic samples (25).…”

“…However, these techniques are still considered to be in the developmental stage due to limited substantive validation and reliability testing. Most of these methods also make use of the bulk soil sample for analysis, which is impractical for some soils that have minimal variation in their bulk chemistry, such as quartz sands, like those found on the Swan Coastal Plain, which require more detailed examinations (24,25).…”