PhD: The fate of microplastics in aquatic environments : Effect of Size, Shape, and Density via FindAPhD

University of Warwick

Warwick, United Kingdom 🇬🇧

About the Project

Project Highlights:

Refining a brand new novel method, developed by the applicants to track and analyse microplastics (Cook et al., 2020)

• Mesocosms studies to track behaviour of microplastics in aquatic flow domains (Rivers, Coastal, Ponds & Wetlands)   

• Training in a wide range of ecological methods using state-of-the-art technology 


Microplastics (MPs) are an emerging contaminant of increasing concern that are ubiquitous within freshwater and marine ecosystems. Rivers are recognised as a fundamental transport pathway for MPs; connecting terrestrial plastic sources to marine ecosystems, as well as an area where high levels of biological activity and modification can occur. However, there is little consideration as to the sources and fate of plastics within these freshwater ecosystems. Rivers are subject to plastic pollution from both point (i.e. sewage systems) and diffuse (i.e. agricultural and urban runoff) sources. It is expected that riverbed sediments act as a sink for microplastic debris (1). However, the extent to which riverbeds interact with MPs and their entrapment rates will be governed by many physical, biological and chemical factors. Colonisation studies of plastic debris by microbial biofilms have shown to cause buoyant polymers to sink (2,3). Equally, microbial biofilms over riverbed sediment will influence MP infiltration and settling rates. Nevertheless, the relative importance of these processes remains largely unclear with empirical data urgently needed to parametrise models. In this project you will investigate the interactions and feedbacks between riverbed dynamics and MPs. The research will build on a brand new novel tracking methodology developed by the applicants (Cook et al., 2020), which allows real time tracking of microplastics in purpose built experimental flumes.

The main aim will be to determine

the key variables which contribute to the entrapment and resuspension of MPs within this freshwater ecotone. Different types of plastic particles with different size, shape & densities will be considered and analysed using novel state-of the-art technology and innovative methods. The release rate and sources of MPs is vital for a more complete understanding and assessment of the hazards posed by these contaminants. As such, the new insights offered by the project have the potential to contribute directly towards new policies relating to water management and environmental conservation.


We will use our novel mesocosm systems to investigate and isolate the different mechanistic processes governing the interaction between the riverbed and MPs. We will test different plastic polymers, with a range of densities and sizes, across a range of riverbed systems with unique characteristics (i.e. pore size, biofilm coated, bedform shape). Methods will include metagenomics to analyse biofilm community structure and optical spectral imaging to visualise where the biofilm colonises the different plastic polymers. In addition, we will adopt our newly developed method to track the movement of MPs within our laboratory-based system (4) using fluorescence-based technology.

Training and skills:

Training will be provided by the supervisory team in a wide range of environmental science approaches and techniques including environmental river processes, molecular techniques (16S amplicon sequencing), bioinformatics, molecular spectroscopy and multivariate data analysis.

Partners and collaboration:

The student will have a training placement at Thames 21, an environmental NGO operating in London, delivering environmental pollution

management with communities and municipal stakeholders. There will be the opportunity to work closely with the Thames 21 team in their river catchment sites around London; collecting river sediment cores and exploring plastic management solutions.

Possible timeline:

Year 1: Mesocosm and biofilm community studies to develop process level understanding of the environmental pathways and interactions of


Year 2: Targeted extraction and analysis of microplastics from riverbed cores to investigate their environmental fate and temporal /

spatial distribution

Year 3: Integration and ecological interpretation

Supervisory Team:

Jonathan Pearson, School of Engineering, University of Warwick

Gary Bending, School of Life Sciences, University of Warwick

Soroush Abolfathi, School of Engineering, University of Warwick

Funding Notes

From the 2021/22 academic year UK Research and Innovation (UKRI) funding is open to both UK and International research students as detailed on the UKRI website. Awards for both Home students and International students cover Home level tuition fees and provide a stipend at the standard UKRI rate to support living costs. International students should note that UKRI will not fund the difference in Home level tuition fee and International level tuition fee. Funding for this may be available from other sources but specific guidance on this is currently not available. Please watch out for updated information on our website.


1. Rillig, M.C., 2012. Microplastic in terrestrial ecosystems and the soil? Environmental Science and Technology 46, 6453-6454.
2. Rummel, C.D., Jahnke, A., Gorokhova, E., Kuhnel, D., Schmitt-Jansen, M, 2017. Impacts of biofilm formation on the fate and potential effects of microplastic in the aquatic environment. Environmental Science & Technology Letters, 4, 258-267.
3. Kaiser, D., Kowalski, N., Waniek, J.J, 2017. Effects of biofouling on the sinking behavior of microplastics. Environmental Research Letters, 12, 124003.
4. Cook, S., Chen, H.L., Abolfathi, S., Bending, G.D, Schäfer, H., Pearson, J.M. Quantifying microplastic transport in aquatic flows using fluorometric techniques, Volume 170, 1 March 2020, 115337
5. Merel Kooi* and Albert A. Koelmans,2019. Simplifying Microplastic via Continuous Probability Distributions for Size, Shape, and Density. Environ. Sci. Technol. Lett. 2019, 6,