Bayesian sediment fingerprinting provides a robust tool for environmental forensic geoscience applications
Ingrid F. Small, John S. Rowan, Stewart W. Franks, Adam Wyatt, Robert W. Duck, 2004. "Bayesian sediment fingerprinting provides a robust tool for environmental forensic geoscience applications", Forensic Geoscience: Principles, Techniques and Applications, K. Pye, D. J. Croft
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Sediment fingerprinting is an approach for the quantitative determination of sediment provenance (both spatial sources and types of sediment supply) over a range of temporal and spatial scales. Though widely adopted, studies often vary in their attention to the underlying assumptions and in their treatment of modelling uncertainty. A Bayesian approach to the multivariate problem of ‘unmixing’ sediment sources is reported, showing the significance of source group variability and source group sampling density to the accuracy of model output. The model produces results as median source group contributory coefficients (and associated 95% quantiles). The model was applied to environmental data obtained from selected soil erosion studies reported within the peer-reviewed literature. Good correspondence (r2=0.89) between reported mean source group contributory coefficients and median values were found when recalculated using the Bayesian analysis. However, confidence levels are highly variable, ranging from 2% to 97%. The robustness of any unmixing solution depends on factors such as the number of samples, the number of source groups and the variance of source group properties. It is concluded that ‘forensic-style’ investigations must recognize these uncertainties and be appropriately resourced to achieve tolerable accuracy and precision. The discussion considers additional confounding factors such as non-conservative tracer behaviour and enrichment/depletion during the sediment delivery process.
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Forensic Geoscience: Principles, Techniques and Applications
Forensic geoscience is an increasingly important sub-discipline within geoscience and forensic science. Although minerals, soils, dusts and rock fragments have been used as only begun to be recognized in the last ten years or so. The police and other investigative bodies are keen to encourage such developments in the fight against crime, particularly since many criminals show a high level of forensic awareness with regard to evidence such as fingerprints, blood and other body fluids. The papers in this volume illustrate some of the main principles, techniques and applications in current forensic geoscience, covering research and casework in the UK and internationally. The techniques described range from macro-scale field geophysical investigations to micro-scale laboratory studies of the chemical and textural properties of individual particles. In addition to forensic applications, many of these techniques have broad utility in geological, geomorphological, soil science and archaeological research.