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Recolha de amostras palinológicas em viaturas acidentadas : identificação taxonómica e molecular de palinomorfos no contexto forense
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O presente estudo teve por objetivo a avaliação do potencial da Palinologia Forense na caracterização ambiental a partir de superfícies automóveis, recorrendo à análise morfológica e molecular de poeiras recolhidas em cinco viaturas com origens geográficas distintas. A análise morfológica, realizada por microscopia ótica e microscopia eletrónica de varrimento, permitiu identificar 33 táxons distintos e revelou perfis polínicos marcadamente influenciados pelas condições ecológicas regionais, pela fenologia das espécies anemófilas e pelos percursos quotidianos das viaturas. Os géneros Quercus, Pinus, Olea, Prunus, Juniperus, Rumex e Urtica foram particularmente recorrentes, constituindo indicadores robustos da vegetação predominante entre janeiro e abril. Os Índices de Similaridade (IS) obtidos em de cada viatura evidenciaram que as diferentes zonas analisadas apresentavam composições polínicas muito semelhantes (valores maioritariamente >80%), indicando uma deposição uniforme das partículas entre zonas estruturais distintas. A comparação inter-viaturas revelou igualmente uma forte semelhança na composição do pólen, refletindo a presença de um fundo aerobiológico comum, associado às condições atmosféricas predominantes na região centro-sul de Portugal.
Em contraste, a análise molecular das seis amostras submetidas a sequenciação da região ITS2 apresentou resultados inconclusivos, com predomínio de sequências fúngicas e ausência de correspondência com a composição polínica observada microscopicamente. A baixa deteção de ADN vegetal, constituiu uma limitação determinante para a interpretação taxonómica dos dados moleculares. Estes resultados sugerem a necessidade de implementação de etapas de pré-processamento destinadas à remoção dos fungos, como por exemplo, filtração, ou em alternativa, a utilização de primers mais específicos para espécies vegetais. Apesar destas limitações, a análise morfológica demonstrou elevada eficácia na discriminação espacial das viaturas, confirmando a aplicabilidade da palinologia forense como ferramenta complementar na reconstrução de trajetos e na associação de objetos a contextos geográficos específicos.
The aim of this study was to evaluate the potential of forensic palynology in environmental characterisation based on vehicle surfaces, using morphological and molecular analysis of dust collected from five vehicles with different geographical origins. Morphological analysis, conducted using optical microscopy and scanning electron microscopy, enabled the identification of 33 different taxa and revealed pollen profiles strongly influenced by regional ecological conditions, the phenology of anemophilous species, and the daily routes travelled by each vehicle. The genera Quercus, Pinus, Olea, Prunus, Juniperus, Rumex, and Urtica were particularly recurrent, serving as robust indicators of the predominant vegetation between January and April. The Similarity Indices (SI) obtained for each vehicle showed that the different areas analysed had very similar pollen compositions (values mostly >80%), indicating uniform deposition of particles between different structural areas. The inter-vehicle comparison also revealed a strong similarity in pollen composition, reflecting the presence of a common aerobiological background associated with the prevailing atmospheric conditions in south-central Portugal. In contrast, molecular analysis of the six samples submitted to ITS2 region sequencing presented inconclusive results, with a predominance of fungal sequences and no correspondence with the pollen composition observed microscopically. The low detection of plant DNA was a determining limitation for the taxonomic interpretation of the molecular data. These results suggest the need to implement pre-processing steps aimed at removing fungi, such as filtration, or alternatively, the use of more specific primers for plant species. Despite these limitations, morphological analysis proved highly effective in the spatial discrimination of vehicles, confirming the applicability of forensic palynology as a complementary tool in the reconstruction of routes and the association of objects with specific geographical contexts.
The aim of this study was to evaluate the potential of forensic palynology in environmental characterisation based on vehicle surfaces, using morphological and molecular analysis of dust collected from five vehicles with different geographical origins. Morphological analysis, conducted using optical microscopy and scanning electron microscopy, enabled the identification of 33 different taxa and revealed pollen profiles strongly influenced by regional ecological conditions, the phenology of anemophilous species, and the daily routes travelled by each vehicle. The genera Quercus, Pinus, Olea, Prunus, Juniperus, Rumex, and Urtica were particularly recurrent, serving as robust indicators of the predominant vegetation between January and April. The Similarity Indices (SI) obtained for each vehicle showed that the different areas analysed had very similar pollen compositions (values mostly >80%), indicating uniform deposition of particles between different structural areas. The inter-vehicle comparison also revealed a strong similarity in pollen composition, reflecting the presence of a common aerobiological background associated with the prevailing atmospheric conditions in south-central Portugal. In contrast, molecular analysis of the six samples submitted to ITS2 region sequencing presented inconclusive results, with a predominance of fungal sequences and no correspondence with the pollen composition observed microscopically. The low detection of plant DNA was a determining limitation for the taxonomic interpretation of the molecular data. These results suggest the need to implement pre-processing steps aimed at removing fungi, such as filtration, or alternatively, the use of more specific primers for plant species. Despite these limitations, morphological analysis proved highly effective in the spatial discrimination of vehicles, confirming the applicability of forensic palynology as a complementary tool in the reconstruction of routes and the association of objects with specific geographical contexts.
Descrição
Dissertação para obtenção do grau de Mestre no Instituto Universitário Egas Moniz
Palavras-chave
Palinologia forense Grãos de pólen Análise morfológica Análise molecular ITS2 Viaturas Bioindicadores Deposição atmosférica Caracterização ambiental Índice de similaridade