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Measurements of the scattering characteristics of sediment suspensions with different mineralogical compositions

By Benjamin D. Moate and Peter D. Thorne

Abstract

Acoustic studies of suspended sediments often assume the dominant mineral in suspension is quartz, the density and intrinsic scattering properties of which are implemented when inverting acoustic backscatter data collected at sea. However, compositional analysis studies of suspended and sea-bed particulate material show a wide range of mineral species contribute to the inorganic fraction of sediments in the marine environment. Whilst no theoretical framework exists to predict the acoustic properties of irregularly shaped sediment grains, the density, compressional, and shear wave velocities of common marine mineral species can vary by up to a factor of two. In this study, we present and compare measurements of the intrinsic scattering parameters, namely the normalized total scattering cross section, χ, and the backscatter form function, f, obtained from homogenous suspensions of irregularly shaped sand sized grains of both magnetite and quartz. Our preliminary measurements suggest that in the geometric scattering regime, χ is enhanced for magnetite sands by ~ 100 % relative to quartz. Similarly, measurements of the form function for magnetite sands are enhanced by ~ 33 % relative to quartz in the geometric regime, though no measurable difference was observed in the Rayleigh regime. The implications of these results for acoustic backscatter data collected at sea are discussed

Topics: Marine Sciences
Publisher: F.O.R.T.H.
Year: 2009
OAI identifier: oai:nora.nerc.ac.uk:8506

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