Spatial and temporal environmental pollen analysis of footwear worn in the area of Barcelos, North-West Portugal, in a forensic context

摘要

In this work, we performed a palynological analysis of soil sampled from the footwear in order to provide their spatial and temporal classification. The sampling was performed in the shoes of 20 volunteers, in two different periods: autumn-winter and spring 2016/2017. The volunteers belonged to the same geographic region within a radius of 500 m. During the laboratorial treatment, the pollinic content present in the shoes sole was concentrated applying several treatments to destroy the exogenous material. A hierarchical cluster analysis was performed to verify whether it was possible to distinguish the samples based on their pollen assemblages. All the samples showed pollinic content, even when the shoes were apparently clean. The pollen types found were similar across the sampling period although with different pollen assemblages. In the winter samples, there was a prevalence of Fraxinus, Myrtaceae, Pinaceae (mostly Cedrus) and Poaceae pollen, while in the spring pollen of Olea, Poaceae, Pinaceae (namely Pinus) and Quercus was observed. Our results also demonstrated the discrimination between close sites (approximately 200 m), showing that the use of palynological analysis in footwear allows the collection of temporal and spatial information that can be used in forensic investigations.