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The fate of microplastics in aquatic environments


   School of Life Sciences

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  Dr J M Pearson  No more applications being accepted  Competition Funded PhD Project (Students Worldwide)

Warwick United Kingdom Bioinformatics Marine Biology Marine Sciences Molecular Biology Pollution

About the Project

Project Highlights:

  • Hone novel methods to track (real-time) and analyse microplastics
  • Design mesocosms to study the behaviour of microplastics in riverbed sediments
  • Training in a wide range of ecological methods using state-of-the-art technology 

Overview:

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 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 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.

Methodology:

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, and baseline the MPs results against traditional regulatory approved fluorometric solute tracing techniques. It is important to apply our understanding to the real-world environment. As such, we will also use local rivers and sites across London as a ‘living laboratory’ to collect sediment cores from the river bed & perform regulatory approved tracing tests. 

Training and skills:

Students will be awarded CENTA2 Training Credits (CTCs) for participation in CENTA2-provided and ‘free choice’ external training. One CTC equates to 1⁄2 day session and students must accrue 100 CTCs across the three years of their PhD.

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

Partners and collaboration (including CASE):

The PhD researcher 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 sediment cores and exploring plastic management solutions.

COVID-19 Resilience of the Project:

Although the proposed project will principally based in a physical laboratory (with large scale flumes), we also have instrumented field sites available (e.g. https://www.youtube.com/watch?v=wwQJKMNKbgA, with specialist measurement equipment) if Covid dictates that indoor laboratory work is no longer possible. 

Possible timeline:

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

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


Funding Notes

Home (UK) students who have been ordinarily resident in the UK for at least three years can apply for full awards covering tuition fees and annual stipend for living costs.
International students (including EU Students) can apply for jointly funded awards covering tuition fees in full and annual stipend for living costs.
Successful International candidates would need to cover all other costs themselves including Health Surcharge, visa and flights.

References

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, Water Research (in review).
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