Longitudinal dispersion of microplastics in aquatic flows using fluorometric techniques

Sarah Cook,Hui-Ling Chan,Soroush Abolfathi,Gary D Bending,Hendrik Schäfer,Jonathan M Pearson

doi:10.1016/j.watres.2019.115337

Sarah Cook, Hui-Ling Chan + Show 4 more

Open Access

https://doi.org/10.1016/j.watres.2019.115337

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Abstract

Microplastics are an emerging environmental contaminant. Existing knowledge on the precise transport processes involved in the movement of microplastics in natural water bodies is limited. Microplastic fate-transport models rely on numerical simulations with limited empirical data to support and validate these models. We adopted fluorometric principles to track the movement of both fluorescent dye and florescent stained microplastics (polyethylene) in purpose-built laboratory flumes with standard fibre-optic fluorometers. Neutrally buoyant microplastics behaved in the same manner as a solute (Rhodamine) and more importantly displayed classical fundamental dispersion theory in uniform open channel flow. This suggests Rhodamine, a fluorescent tracer, can be released into the natural environment with the potential to mimic microplastic movement in the water column.

Highlights

Microplastics are an emerging environmental contaminant and are increasingly detected in freshwater environments (Jambeck et al, 2015; Lebreton et al, 2017; Dris et al, 2018; Eriksen et al, 2018)
Experimental studies have shown PE to be a vector for organic contaminants through absorption (Teuten Emma et al, 2009; Seidensticker et al, 2018) making the need to understand the movement of these microplastics of increased importance
We show that a harmless fluorescent tracer, which can be safely released into the natural environment, has the potential to be used a proxy for the movement of neutrally buoyant microplastics in uniform open channel flow

Summary

Introduction

Microplastics (defined as plastic particles < 5 mm) are an emerging environmental contaminant and are increasingly detected in freshwater environments (Jambeck et al, 2015; Lebreton et al, 2017; Dris et al, 2018; Eriksen et al, 2018) These contaminants originate from either primary or secondary sources (Boucher and Froit, 2017). Secondary sources originate from the breakdown of large ‘macro’ plastics largely by weathering processes, including photodegradation which intensifies polymer abrasion (Gewert et al, 2015; Boucher and Froit, 2017; Rummel et al, 2017) These emerging contaminants have gained increased interest from society, the scientific community and policymakers, yet there is little understanding as to the environmental fate and behaviour of microplastics within fluvial systems (Kooi et al, 2018). This presents a challenge in validating models which can adequately capture their hydrodynamic behaviour in lotic ecosystems

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