Stanton, Thomas
(2020)
A spatio-temporal record of microplastic particles and natural textile fibres in the River Trent and its tributaries, and in atmospheric deposition across the Trent catchment.
PhD thesis, University of Nottingham.
Abstract
Extended Abstract
Context
The study of microplastic (<5 mm) pollution has, over the past 15 years, emerged as an emotive topic of environmental concern. The environmental impacts of microplastic particles are known to be varied and potentially severe. Freshwater systems are known to be pathways for the transport of microplastic particles from their sources, ultimately to the marine environment. Despite this, efforts to study freshwater microplastic pollution have been limited by the methodological approaches taken to collect and process samples, and identify particles within them. Many freshwater microplastic studies are therefore unable to provide a comprehensive assessment of their concentrations.
This thesis presents a systematic and objective assessment of freshwater and airborne microplastic pollution in and around the River Trent across Staffordshire, Nottinghamshire and Leicestershire.
Methods
Microplastic pollution was quantified in three rivers and in atmospheric deposition across the Trent Catchment, UK. Over a 12 month period, freshwater samples were collected every four weeks on the Rivers Trent, Leen, and Soar, and in atmospheric deposition at four sites across the University of Nottingham’s UK campuses every two weeks.
This sampling campaign was supported by robust techniques to categorise microplastic particles isolated from environmental samples. This included the development of a comprehensive methodology for the categorisation of textile fibres, and a thorough assessment of the use of Nile red in microplastic quantification.
Results
This work has identified microplastic particles at all freshwater and atmospheric sites sampled. However, the concentrations of microplastic particles quantified in this research have been some of the lowest recorded in literature; not once exceeding 0.4 particles / L across the freshwater sampling network. The systematic nature of this sampling campaign has generated the one of the most temporally comprehensive dataset of any freshwater microplastic sampling campaign. By assessing temporal variation this work has identified the extent to which previous freshwater microplastic extrapolations reported in peer reviewed literature could have been misleading.
Furthermore, the methodological developments in the identification of microplastic particles made during the course of this work cast doubt on the findings of previous studies that have relied on the visual identification of microplastic textile fibres, and those that have used Nile red in microplastic quantification.
Main conclusions
Microplastic particles are one of many anthropogenic pressures on environmental systems, and there is a need for pragmatic assessment of their prevalence. Without temporal sampling, freshwater microplastic studies are unlikely to be representative of the bodies of water sampled. Moreover, the methodologies employed to identify microplastic particles in environmental samples are subject to unquantified levels of error. The categorisation of textile fibres in particular has also provided further evidence to support emerging concerns for the potential ecological harm of natural textile fibres such as cotton and wool, alongside their plastic analogues.
Environmental concern for the ubiquity of microplastic pollution is well founded, and efforts to minimise microplastic emission should be encouraged. However, the research presented in this thesis highlights the importance of robust methodologies in microplastic sampling and identification, and recognises the need for objectivity in the interpretation and dissemination of microplastic research.
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