Simultaneous Thermal Analysis (STA): A Powerful Tool for Forensic Investigation of Geomaterials

Discrimination Efficiency of Thermogravimetry and Differential Scanning Calorimetry in Soil Forensics

“…When submitted to the thermal analysis, thermogravimetry (TG) and differential scanning calorimetry (DSC) curves represent the mineralogical transformations in soil samples at respective temperatures (Figure 2). The removal of crystal-adsorbed and structural water are the main outcomes resulting from thermal decomposition of minerals [13]. Water in hydrate minerals is released according to different kinetics and mechanisms, depending on the type of mineral examined [13,18].…”

“…The soil sampling design involved a triangular arrangement with samples positioned 1 m apart within each group, ensuring a minimum separation of 10 km between distinct groups, as shown in Figure 1. A total of ninety soil samples were collected, air-dried under shaded conditions, and passed through a 270 mesh sieve to remove sand particles ≥ 53 µm; sand has been shown to be unsuitable for forensic investigations of tropical and subtropical soils [13,16]. An eight-channel quarter was employed to homogenize samples, and three partitions were selected to obtain approximately 10 g of soil from each soil sample.…”

“…The dehydroxylation-induced mass reduction caused by thermal decomposition enabled the estimation of the percentual concentrations of gibbsite (Gb), goethite (Gt), and kaolinite (Kt), the predominant minerals in the selected tropical soils. In the process, mineral-bound water is removed by dehydroxylation, which causes a reduction in the mass of the analyzed samples, which can be measured from the thermogravimetric curve [13].…”

“…Minerals are one the main constituents of soils, they imprint relatively permanent features in them, and these characteristics are essential in forensic investigations [2,6,8,13]. Thermal analysis techniques like TG and DSC play a paramount role in the mineralogical characterization of soils, as minerals show physical and chemical variations in their properties when subjected to heating.…”

“…TG measures changes in mass as a function of temperature variation, and it can provide important information on the mineralogical composition of soils, thanks to the presence of several thermally active phases like phyllosilicates. DSC measures the energy differences during the analysis, and the resulting thermogram provides a calorimetric analysis of the process even when sample quantities are as small as a few milligrams [13].…”