Chemometric study on the forensic discrimination of soil types using their infrared spectral characteristics (original) (raw)
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The forensic analysis of soil organic by FTIR
Forensic Science International, 2000
In order to elucidate the discriminating power of various soil analytical techniques, over 100 soils samples were analyzed using conventional analysis (i.e., color, percent organic and density gradient) and a novel FTIR technique. The FTIR technique involves collecting a spectrum of a soil sample that has been oxidatively pyrolysed, and therefore all organic have been degraded. This spectrum is subtracted from the spectrum of the same sample that contained the organic prior to pyrolysis. This resultant IR spectrum represents the organic portion of the sample. The use of organic components increases the discrimination in soils that are otherwise similar. We have illustrated the usefulness of this technique by selecting four soil samples, which have identical Munsel color values but can be discriminated by subtractive ETIR. We propose that the ETIR spectra of the organic portion of soil serves a useful purpose in forensic investigations.
Forensic Science International, 2002
Forty-four soil samples from five different areas were examined on the basis of the UV-Vis spectrum of the acid fraction of humus with a view to achieving good discrimination between them. Fulvic and humic acids were extracted from the samples into an alkaline aqueous solution and absorbance values, after appropriate transformations, were subjected to a K-mean cluster analysis (CA) over the objects (samples) for an initial feature reduction (20 variables retained). This was followed by principal component analysis (PCA) for the removal of outliers (four samples removed). The same statistical technique was used on the remaining samples to decide how many variables to enter into the linear discriminant function analysis (DA) and whether original variables or component scores should be used. It was found that the scree test was a good criterion for deciding on the number of components to extract (nine components extracted) and that the use of component scores instead of original variables led to a lower average redundancy (20.6%) of the variables in the discriminant model. From the components entered into the model and their loadings, it was concluded that the discrimination achieved was due to the relative concentration of aromatic groups and other fragments in the samples as well as the degree of soil humification. An overall 85% correct classification of the training dataset was observed (Wilks' l ¼ 0:0420) and the method was judged satisfactory for supporting exclusionary forensic purposes. #
Spectral analysis as an extra method to soil type discrimination
Agricultural Science and Technology, 2020
The purpose of the study was to test near infrared soil spectra as an extra method for three soil types (Fluvisols, Vertisols and Solonchaks) discrimination from different regions of South Bulgaria. The diffuse reflectance spectra of 177 soil samples (from the 0-20cm layers): 50 samples of Fluvisols soil type, 78 samples of Vertisols soil type and 48 samples of Solonchaks soil type were obtained using a Spectrum NIRQuest (OceanOptics, Inc.) working within the range from 900 to 1700 nm. Soft independent modelling of class analogy (SIMCA) was performed to classify samples according to their taxonomic classes. The results obtained showed that the soil samples are separated accurately according to their soil type based on their spectral information. All this could be used in the future studies related to the application of the NIRS method as a qualitative or quantitative method for soil analysis and also for the purposes of precision farming.
Systematic Approaches For Soil Analysis In Forensic Investigation
In forensic science, soil can be one of the valuable evidence during investigations. Soils might link an individual to a crime scene as soil transferred in a mud stabbing to footwear, tires, soil marks on vehicles, traces left on clothes can correlate the presence or absence of this person on a particular scene of the crime. The soil has extreme complexity not only in components but also in physical nature such as sediment, color, and structure. The aim of the present study was to investigate various physico-chemical properties of different types of soils. These soil properties can be beneficial in forensic investigations along with other evidences found in a crime scene. A number of experiments have been performed to achieve our goal. Particle Size Distribution Analysis PSDA was performed to differentiate between several soil samples based on their texture, through estimation of the size fractions of clay, silt and sand. A hydrometer method was used to estimate the percentages of sand, silt and clay in six samples of soils. We could allocate the soil samples to a textural class that helped us to define the type of soil and link this to a special location. Several soils were analyzed for organic matter content, ammonium, nitrate, carbonates, bicarbonates, chloride, calcium and magnesium in the soil samples. The high variability in results among the tested samples could refer to a unique fingerprinting for each soil type which is vital findings for forensic soil investigations in a crime scene.
Talanta, 2020
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Investigations into Soil Composition and Texture Using Infrared Spectroscopy (2–14 μ m)
Applied and Environmental Soil Science, 2012
The ability of thermal and shortwave infrared spectroscopy to characterise composition and texture was evaluated using both particle size separated soil samples and natural soils. Particle size analysis and separation into clay, silt, and sand-sized soil fractions was undertaken to examine possible relationships between quartz and clay mineral spectral signatures and soil texture. Spectral indices, based on thermal infrared specular and volume scattering features, were found to discriminate clay mineral-rich soil from mostly coarser quartz-rich sandy soil and to a lesser extent from the silty quartz-rich soil. Further investigations were undertaken using spectra and information on 51 USDA and other soils within the ASTER spectral library to test the application of shortwave, mid-and thermal infrared spectral indices for the derivation of clay mineral, quartz, and organic carbon content. A nonlinear correlation between quartz content and a TIR spectral index based on the 8.62 μm was observed. Preliminary efforts at deriving a spectral index for the soil organic carbon content, based on 3.4-3.5 μm fundamental H-C stretching vibration bands, were also undertaken with limited results.
The 5th Innovation and Analytics Conference & Exhibition (IACE 2021)
Nowadays, the increasing population urged us to have soil quality determination techniques that can be conducted on-site, inexpensive, and much more rapid resulting in cost savings and faster decisions. Traditionally, the method that uses capillary Gas Chromatography/ Flame Ionization Detector (GC/FID) is time-consuming and expensive. This study evaluates the performance of the current practice, Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy, coupled with multivariate modelling methods, to analyse soil samples. Partial least square regression (PLSR) and partial least square-discriminant analysis (PLS-DA) methods were implemented using soil spectra obtained to predict soil properties consisting of sand and clay plus classify the soil type. Using the PLS-DA method, the classification of soil types shows a promising result with the area under the receiver operating characteristic curve (AUC) of 0.95, meaning that the model is a very good classifier. This study demonstrates the potential of using the PLS-DA method in DRIFT spectroscopy to be a rapid and accurate method in classifying the soil type. However, moderate accuracy in PLSR analysis needs further investigation and exploration in sample size and methodology.
Soil organic characterisation in forensic case work
Episodes
Soils are composed of natural inorganic and organic (both natural plant and animal and also man-made) components. The organic soil profile is complex, and there is a range of analytical methods available; however, the organic characteristics strongly complement that of the soil inorganic profile characteristics to provide a complete soil analytical profile, allowing detailed comparison and evaluation of soil recovered from questioned items with soil at a crime scene and to also provide clues in crime reconstruction and in search operations. Organic profiles can provide information about a range of soil forming features such as the vegetation present, land use past and present, altitude, etc., as well as providing information about nearness to industry and roads, tracks and rail networks and infrastructure. Biomarkers which remain in soil as a result of body decomposition can also be analysed and used in search and to help locate human remains.