Pollution, plastics and plumes: understanding the behaviour of microplastics in aquatic sediments


Microplastic burden in aquatic environments is now recognised as a potential threat to human and environmental health. Although microplastic transfer to the ocean from the terrestrial river network contributes up to 90% of the plastics in the oceans the factors controlling the mobilization, transport and ultimately fate within the environment remain largely unconstrained. In rivers, microplastics are stored within sediment beds and as such are likely controlled by the same physical processes governing the movement of sediment.  For example, physical factors related to the flow regime are likely to be a first order control on the transport of plastics. Given that the climate change forecast is for a greater number of higher magnitude, more frequent floods, we need to know how rivers will respond so as to mitigate against the potential for contaminant remobilisation in the future. Biophysical factors such as the growth of biofilms on plastic particles are also likely to be key controls on plastic mobility since biofilm growth on river sediments has been shown to increase a particle’s resistance to entrainment; the effects of such biostabilisation on microplastic flux has not yet been considered. This is despite the fact that biofilm growth can change the buoyancy, surface characteristics and aggregation properties of the plastic particles such as to cause them to be deposited rather than transported and hence increase their residence time.

The successful candidate will work with the project team to refine the project aims but will work towards generating a new, quantitative understanding regarding the controls of microplastic mobilization, transport and fate within river systems. To do this an integrated approach that combines laboratory experiments and field work will be used. Laboratory experiments will use the flume facilities at Liverpool to test the impact of flow regime characteristics on bed erosion. The sediment bed will be seeded with microplastics and exposed to different flow regimes. High resolution laser scanning of the sediment bed will be directly coupled with turbulent flow data to begin to understand how the properties of the sediment bed interact with the flow to control the flux of plastics. Sediment cores taken during the experiments will be analysed using the 3D CT scanner at Liverpool to establish the changes to the contaminant profile. Laboratory experiments will be validated by fieldwork undertaken as necessary across the Mersey to quantify relationships between bed turnover rate and the flow regime under natural hydrodynamic settings.

Applicant Eligibility

Candidates will have, or be due to obtain, a Master’s Degree or equivalent from a reputable University in an appropriate field of Engineering.  Exceptional candidates with a First Class Bachelor’s Degree in an appropriate field will also be considered. 

Application Process

Candidates wishing to apply should complete the University of Liverpool application form applying for a PhD in Civil Engineering and uploading: Degree Certificates & Transcripts, an up to date CV, a covering letter/personal statement and two academic references. 


Candidates wishing to discuss the research project should contact the primary supervisor, those wishing to discuss the application process should discuss this with the School PGR Office (soepgr@liverpool.ac.uk).