Microplastic and natural sediment in bed load saltation: material does not dictate the fate
File(s)
Published version
OA Location
Author(s)
Lofty, J
Valero, D
Wilson, CAME
Franca, MJ
Ouro, P
Type
Journal Article
Abstract
Microplastic (MP) pollution is a well document threat to our aquatic and terrestrial ecosystems, however, the mechanisms by which MPs are transported in river flows are still unknown. The transport of MPs and natural sediment in aquatic flows could be somewhat comparable, as particles are similar in size. However, it is unknown how the lower density of MPs, their shape and their different material properties impact transport dynamics. To answer this, novel laboratory experiments on bed load saltation dynamics in an open-channel flow, using high-speed camera imaging and the detection of 11,035 individual saltation events were used to identify the similarities and differences between spherical MPs and spherical natural sediments transport. The tested MPs and sediment varied in terms of size and material properties (density and elasticity). Our analysis shows that the Rouse number accurately describes saltation length, height, transport velocity and collision angles equally well for both MPs and natural sediments. Through statistical inference, the distribution functions of saltation trajectory characteristics for MPs were analogous to natural sediment with only one sediment experiment (1.4% of cases) differing from all other plastic experiments. Similarly, only nine experiments (9.3% of cases) showed that collision angles for MPs differed from those of natural sediment experiments. Differences observed in terms of restitution become negligible in overall transport dynamics as turbulence overcomes the kinetic energy lost at particle-bed impact, which keeps particle motion independent from impact. Overall, spherical MP particles behave similarly to spherical natural sediments in aquatic environments under the examined experimental conditions. This is significant because there is an established body of knowledge for sediment transport that can serve as a foundation for the study of MP transport.
Date Issued
2023-09-01
Date Acceptance
2023-07-07
Citation
Water Research, 2023, 243
ISSN
0043-1354
Publisher
Elsevier
Journal / Book Title
Water Research
Volume
243
Copyright Statement
© 2023 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/37453401
PII: S0043-1354(23)00765-0
Subjects
Bedload
BEHAVIOR
COLLISION
Engineering
Engineering, Environmental
Environmental Sciences
Environmental Sciences & Ecology
GRAINS
INGESTION
Life Sciences & Biomedicine
Micro plastic
PARTICLES
Physical Sciences
Plastic density
Plastic transport
PROFILES
River pollution
Rouse number
Science & Technology
Technology
TRANSPORT
Water Resources
Publication Status
Published
Coverage Spatial
England
Article Number
120329
Date Publish Online
2023-07-08