Andreia Rodrigues

Characterization of soils from the Algarve region (Portugal): A multidisciplinary approach for forensic applications

The Algarve is located at a very short distance from North Africa, in Southern Portugal, and as one of the most touristic regions of Portugal, it is accessible by air, land and sea. It is very susceptible to many illegal activities, such as illegal migration, drug trafficking, kidnapping, and murder, among others. Therefore, an Algarve soils database for forensic purposes is being conducted with the conjunction of geological and palynological methodologies on soils characterization, since this is of fundamental importance to assess reliable evidence on forensic investigations. In this study, the properties of soils from several proximate sites from the Algarve were investigated, namely: (i) colour determined by spectrophotometry; (ii) particle size distribution determined by laser granulometry; (iii) low-field magnetic susceptibility by a susceptibility meter; and (iv) pollen content using a light microscope. Finally, a hierarchical cluster analysis was applied to ascertain the capacity of the different soil properties for discrimination between samples. The study reveals the utility of geobotanical techniques for forensic discrimination of soils. Even though some similarities between some of the samples were found, each one presented a combination of colour, particle size distribution, magnetic susceptibility and pollen features that enable the determination of a fingerprint expected to reveal a specific site for future selection of coastal search areas in the Algarve region.

The potential application of magnetic susceptibility as a technique for soil forensic examinations

Abstract Magnetic susceptibility measurement methodology, its reproducibility and accuracy of analysis were tested on soil samples to evaluate its potential use in forensic applications. It was observed that magnetic susceptibility can enable discrimination between soil samples, measured values are reproducible over time and the analysis can be carried out on small samples. However, in order for this method to be used in a forensic soil investigation, it is important to always adopt the same analytical protocol during analysis.

Integration of different sediment characteristics to discriminate between sources of coastal sediments

Abstract In order to investigate the effects of geological setting and the surrounding lithology on coastal sediment samples, four properties were analysed in a series of samples collected from different localities: colour determined by spectrophotometry; particle size distribution determined by laser granulometry; chemical composition determined by ICP-MS (inductively coupled plasma mass spectrometry); and low-field magnetic susceptibility determined using a susceptibility meter. A hierarchical cluster analysis was applied to ascertain the capacity of the different properties for discrimination between samples from the different geological settings. The study reveals that colour analysis only allowed discrimination between different geographical areas; particle size distribution allowed separation between dune and beach samples; chemical composition allowed discrimination between both different geological settings and also between dune and beach sands; and, finally, the combination of magnetic susceptibility with colour and particle size distribution allowed for clear discrimination between geological settings, and between beach and sand dunes. The studied samples are part of a larger and growing collection of data, and a more extensive evaluation will continue to be made for a more definitive assessment of the use of different characteristics for discrimination. So far, the results give confidence that it is meaningful to use these characteristics, especially when examined in combination, to distinguish between different locations.