Comparison of spatial, vertical and seasonal distribution of palynomorphs in two Perth metropolitan wetlands

Susan Sirr

    Research output: ThesisMaster's Thesis

    359 Downloads (Pure)


    Forensic Palynology has helped to solve crimes ranging from fraud to murder. Pollen is ubiquitous, almost indestructible and microscopic in size. It is often sticky and easily carried, undetected, from one place to another. As pollen is unique to a plant species, combinations of pollen types (pollen assemblages) present in soil or other samples can identify the type of environment, and often the exact location, from which a sample originated. Although Forensic Palynology has been used routinely in New Zealand for over 25 years, is commonly used in the United Kingdom and has been used in several cases in Australia in the past ten years, little research has been done in this field. In Australia, police require an initial broad palynological analysis of samples from a crime scene prior to approving a more detailed analysis. This project investigates palynological samples from two superficially similar environments that could potentially be a crime scene and alibi location, in order to determine if they can be broadly distinguished from each other. Two Perth metropolitan wetlands, Herdsman Lake and Eric Singleton Bird Sanctuary, were chosen for study as potential sites for assaults and clandestine burials. Four sites within each wetland, with correspondingly similar vegetation communities, were sampled at surface level in different seasons. At three sites, 50 cm cores were taken and sampled at seven levels to simulate shallow grave profiles. Samples were prepared and analysed using standard palynological techniques. Surface and core (grave profile) pollen assemblages were compared site by site within each wetland, and with the corresponding site of the other wetland. The grave profile assemblages for each core were combined and averaged to represent mixed 'burial assemblages', and similarly compared across and within wetlands. Palynological analysis established that the surface soil samples were characteristic of wetland environments. The different vegetation sites in each wetland, and the corresponding vegetation site in the other wetland, were broadly palynologically distinct. The season in which samples were collected was difficult to determine. Grave profile assemblages generally differed from surface samples at each site, and broadly differed across and between the two wetlands, but the differences in the 'burial assemblages' were less marked. The findings of this study confirm that broad palynological analysis can differentiate between two wetlands at surface level and downhole, and that samples at different depths in a grave should be separately analysed. Collection of control samples from similar and possible alibi environments is essential. Caution should be taken when palynologically interpreting the season in which a crime was committed.
    Original languageEnglish
    Publication statusUnpublished - 2007


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