Method for the determination of preferential orientation of marine particles from laser diffraction measurements

Type Article
Date 2020-04
Language English
Author(s) Font Munoz Joan Salvador1, 2, Jeanneret Raphaël3, Tuval Idan4, 5, Basterretxea Gotzon4
Affiliation(s) 1 : IFREMER, French Institute for Sea Research, DYNECO PELAGOS, 29280, Plouzané, France
2 : Université de Brest - UBO/CNRS/IFREMER/IRD, 29238, Brest, France
3 : Laboratoire de Physique de l’Ecole normale supérieure, ENS, Université PSL, CNRS, Sorbonne Université, Université de Paris, F-75005 Paris, France
4 : Dept. of Marine Ecology. IMEDEA (UIB-CSIC). Miquel Marques 21, 07190. Esporles, Balearic Islands, Spain
5 : Dept. of Physics. University of the Balearic Islands, Ctra. Valldemossa Km. 7.5, 07122, Palma, Balearic Islands, Spain
Source Optics Express (1094-4087) (The Optical Society), 2020-04 , Vol. 28 , N. 9 , P. 14085-14099
DOI 10.1364/OE.390388
WOS© Times Cited 3
Abstract

In situ laser diffractometry (LD) is increasingly used in oceanographic studies to estimate sediment transport, particle fluxes and to assess the concentration of marine phytoplankton. It enables an accurate characterization of the size distribution of suspended particles from the scattering signal produced by their interaction with a collimated laser beam. LD reliably reflects the sizes of suspensions dominated by nearly spherical particles; however, when complex particle morphologies dominate the suspension (e.g. phytoplankton) the resulting particle size distribution (PSD) may present significant variations attributed to different factors. In particular, the orientation of non-spherical particles - which abound in the sea – modifies LD measurements of PSDs. While this may be interpreted as a drawback for some studies (i.e. when precise measurement of the volume concentration is required), we propose that detailed analysis of this signal provides information on particle orientation. We use PDMS micropillars with prescribed elliptical cross-sections to experimentally determine the dependence between the spatial orientation of elongated particles and changes in the PSD measured with a LISST laser diffractometer. We show that LD can be used to adequately characterize the different dimensions of the non-spherical particles at specific orientations. Using this property, we describe and validate a method to infer the preferential orientation of particles in the sea. Our study opens new perspectives in the use of in-situ LD in ocean research.

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Font Munoz Joan Salvador, Jeanneret Raphaël, Tuval Idan, Basterretxea Gotzon (2020). Method for the determination of preferential orientation of marine particles from laser diffraction measurements. Optics Express, 28(9), 14085-14099. Publisher's official version : https://doi.org/10.1364/OE.390388 , Open Access version : https://archimer.ifremer.fr/doc/00625/73683/