Comparison of 2D Optical Imaging and 3D Microtomography Shape Measurements of a Coastal Bioclastic Calcareous Sand

Ryan D Beemer; Linzhu Li; Antonio Leonti; Jeremy Shaw; Joana Fonseca; Iren Valova; Magued Iskander; Cynthia H Pilskaln

doi:10.3390/jimaging8030072

Comparison of 2D Optical Imaging and 3D Microtomography Shape Measurements of a Coastal Bioclastic Calcareous Sand

J Imaging. 2022 Mar 14;8(3):72. doi: 10.3390/jimaging8030072.

Authors

Ryan D Beemer¹, Linzhu Li², Antonio Leonti³, Jeremy Shaw⁴, Joana Fonseca⁵, Iren Valova³, Magued Iskander², Cynthia H Pilskaln⁶

Affiliations

¹ Department of Civil and Environmental Engineering, University of Massachusetts Dartmouth, Dartmouth, MA 02747, USA.
² Department of Civil and Urban Engineering, New York University, New York, NY 10012, USA.
³ Department of Computer and Information Science, University of Massachusetts Dartmouth, Dartmouth, MA 02747, USA.
⁴ Centre for Microscopy, Characterisation & Analysis, University of Western Australia, Crawley 6009, Australia.
⁵ Department of Civil Engineering, City, University of London, London EC1V 0HB, UK.
⁶ School for Marine Science and Technology, University of Massachusetts Dartmouth, Dartmouth, MA 02747, USA.

Abstract

This article compares measurements of particle shape parameters from three-dimensional (3D) X-ray micro-computed tomography (μCT) and two-dimensional (2D) dynamic image analysis (DIA) from the optical microscopy of a coastal bioclastic calcareous sand from Western Australia. This biogenic sand from a high energy environment consists largely of the shells and tests of marine organisms and their clasts. A significant difference was observed between the two imaging techniques for measurements of aspect ratio, convexity, and sphericity. Measured values of aspect ratio, sphericity, and convexity are larger in 2D than in 3D. Correlation analysis indicates that sphericity is correlated with convexity in both 2D and 3D. These results are attributed to inherent limitations of DIA when applied to platy sand grains and to the shape being, in part, dependent on the biology of the grain rather than a purely random clastic process, like typical siliceous sands. The statistical data has also been fitted to Johnson Bounded Distribution for the ease of future use. Overall, this research demonstrates the need for high-quality 3D microscopy when conducting a micromechanical analysis of biogenic calcareous sands.

Keywords: 2D particle shape; 3D particle shape; calcareous; carbonate; dynamic image analysis; granulometry; microtomography; particle shape.