Periodic Reporting for period 1 - InMyWaves (Inertial effects on settling of microplastics in turbulent wavy flows)
Reporting period: 2023-09-01 to 2025-08-31
Plastic pollution in rivers, lakes, and oceans is a growing environmental crisis with serious implications for ecosystems, biodiversity, food security, and human health. Every year, millions of tonnes of plastic enter aquatic systems, where they break down into smaller pieces that can persist for decades. These particles do not remain where they enter the water. Instead, they are carried by currents, waves, and turbulence, sometimes traveling long distances before accumulating in coastal zones, river mouths, or the open ocean.
Despite the scale of this challenge, our ability to predict the pathways of plastics in natural waters is limited. Most studies so far have focused on floating plastics or very small particles in idealised turbulence setting. However, these approaches do not capture the complexity of real aquatic environments, where plastics of different shapes, sizes, and densities are influenced by turbulence, current and surface waves. This knowledge gap makes it difficult to model plastic pathways accurately which in turn hampers strategies to mitigate their impact on ecosystems, food safety, and human health..
The InMyWaves project (Inertial effects on settling of microplastics in turbulent wavy flows) set out to address this gap through carefully designed laboratory experiments. The main objectives were to:
1) Identify the particle properties that dominate settling behaviour.
2) Determine how turbulence modifies the settling and dispersion of plastics compared to quiescent flows.
3) Investigate how the combined effects of turbulence and surface waves influence plastic transport.
By answering these questions, the project aimed to provide new knowledge that improves plastic transport models. The long-term goal is to support more reliable predictions of plastic pollution pathways to predict where plastics will accumulate or how quickly they will disperse, helping society to better protect and manage aquatic environments.
Despite the scale of this challenge, our ability to predict the pathways of plastics in natural waters is limited. Most studies so far have focused on floating plastics or very small particles in idealised turbulence setting. However, these approaches do not capture the complexity of real aquatic environments, where plastics of different shapes, sizes, and densities are influenced by turbulence, current and surface waves. This knowledge gap makes it difficult to model plastic pathways accurately which in turn hampers strategies to mitigate their impact on ecosystems, food safety, and human health..
The InMyWaves project (Inertial effects on settling of microplastics in turbulent wavy flows) set out to address this gap through carefully designed laboratory experiments. The main objectives were to:
1) Identify the particle properties that dominate settling behaviour.
2) Determine how turbulence modifies the settling and dispersion of plastics compared to quiescent flows.
3) Investigate how the combined effects of turbulence and surface waves influence plastic transport.
By answering these questions, the project aimed to provide new knowledge that improves plastic transport models. The long-term goal is to support more reliable predictions of plastic pollution pathways to predict where plastics will accumulate or how quickly they will disperse, helping society to better protect and manage aquatic environments.
The project was organised into three research streams.
Particle properties: Experiments with particles of different shapes but identical size, mass, and density showed that the frontal area of a particle is the dominant factor controlling its settling velocity. When particles fall in groups, wake effects can accelerate those that follow.
Turbulence effects: Controlled experiments in a turbulent water channel revealed that while mean settling velocity is not strongly altered by turbulence, particle properties and turbulence scales play a major role in dispersion. An empirical relationship was developed to estimate streamwise dispersion based on particle and turbulence characteristics.
Surface interactions: Although time constraints prevented full investigation of particle–wave interactions, substitute experiments focused on how subsurface turbulence leaves visible imprints at the water surface. The study demonstrated measurable links between turbulence and surface patterns, opening new possibilities for monitoring aquatic flows using surface observations.
Together, these achievements provide a more complete understanding of how plastics behave in realistic flow conditions and deliver several scientific publications, openly available datasets, and innovative measurement methods to help tackle plastic pollution in our natural waters.
Particle properties: Experiments with particles of different shapes but identical size, mass, and density showed that the frontal area of a particle is the dominant factor controlling its settling velocity. When particles fall in groups, wake effects can accelerate those that follow.
Turbulence effects: Controlled experiments in a turbulent water channel revealed that while mean settling velocity is not strongly altered by turbulence, particle properties and turbulence scales play a major role in dispersion. An empirical relationship was developed to estimate streamwise dispersion based on particle and turbulence characteristics.
Surface interactions: Although time constraints prevented full investigation of particle–wave interactions, substitute experiments focused on how subsurface turbulence leaves visible imprints at the water surface. The study demonstrated measurable links between turbulence and surface patterns, opening new possibilities for monitoring aquatic flows using surface observations.
Together, these achievements provide a more complete understanding of how plastics behave in realistic flow conditions and deliver several scientific publications, openly available datasets, and innovative measurement methods to help tackle plastic pollution in our natural waters.
The project delivered several advances beyond current scientific knowledge:
Mechanistic insights: Volumetric measurements provided new understanding of how particle shape and wake dynamics influence settling, moving beyond the simplified laboratory conditions of earlier studies.
Predictive modelling: An empirical expression was developed to estimate how turbulence, particle properties, and flow conditions together affect streamwise dispersion of different shapes and sizes. This represents a step forward in modelling plastic transport in realistic aquatic environments.
Innovative methods: A stereoscopic system based on low-cost GoPro cameras was successfully used for three-dimensional particle tracking. This shows that high-quality measurements can be achieved without relying on expensive scientific cameras, making the approach more accessible worldwide.
Remote sensing potential: The substitute research on free-surface turbulence established clear links between subsurface turbulence and visible surface patterns such as dimples and scars. This opens a new pathway for monitoring aquatic turbulence using remote sensing, where surface observations can serve as indicators of the flow below, avoiding the need of challenging field works.
These results are not only relevant to understanding plastics in the ocean but also have wider applications in sediment transport, nutrient cycling, and industrial processes involving particles in turbulent flows. They also provide a foundation for future integration into large-scale models and for collaboration with environmental monitoring agencies to translate laboratory findings into practical tools.
Mechanistic insights: Volumetric measurements provided new understanding of how particle shape and wake dynamics influence settling, moving beyond the simplified laboratory conditions of earlier studies.
Predictive modelling: An empirical expression was developed to estimate how turbulence, particle properties, and flow conditions together affect streamwise dispersion of different shapes and sizes. This represents a step forward in modelling plastic transport in realistic aquatic environments.
Innovative methods: A stereoscopic system based on low-cost GoPro cameras was successfully used for three-dimensional particle tracking. This shows that high-quality measurements can be achieved without relying on expensive scientific cameras, making the approach more accessible worldwide.
Remote sensing potential: The substitute research on free-surface turbulence established clear links between subsurface turbulence and visible surface patterns such as dimples and scars. This opens a new pathway for monitoring aquatic turbulence using remote sensing, where surface observations can serve as indicators of the flow below, avoiding the need of challenging field works.
These results are not only relevant to understanding plastics in the ocean but also have wider applications in sediment transport, nutrient cycling, and industrial processes involving particles in turbulent flows. They also provide a foundation for future integration into large-scale models and for collaboration with environmental monitoring agencies to translate laboratory findings into practical tools.