Interpreting LISST-100X measurements of particles with complex shape using digital in-line holography

[1] Measurements of suspended sediment volume concentrations, particle size and number density are routinely collected in marine and fresh-water environments with LISST-100X instruments to understand sediment transport, biological processes and fundamental opto-acoustic problems. A LISST-100X was simultaneously deployed with a novel holographic camera (holocam) in UK coastal waters to assess the performance of the laser diffraction technique when measuring natural suspensions. Volume distributions from the LISST-100X, truncated to exclude non-overlapping size bins with the holocam, exhibit an increase in small particles and median particle size is elevated in comparison to the holocam by 20–40%. We observe positive offsets between LISST-100X and holocam number distributions of up to 2 orders of magnitude for particle sizes between 58–218μm, with discrepancies rising to 4 orders of magnitude for finer and coarser sizes. To explain these differences, a novel multiscale representation of particle size is used. The method quantifies individual dimensions that make up any two-dimensional geometrical structure, it can be used as a metric for particle complexity, and offers a plausible explanation for an apparent increase in small particles (