Microplastic contamination of river beds significantly reduced by catchment-wide flooding

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Microplastic contamination of the oceans is one of the world’s most pressing environmental concerns. The terrestrial component of the global microplastic budget is not well understood because sources, stores and fluxes are poorly quantified. We report catchment-wide patterns of microplastic contamination, classified by type, size and density, in channel bed sediments at 40 sites across urban, suburban and rural river catchments in northwest England. Microplastic contamination was pervasive on all river channel beds. We found multiple urban contamination hotspots with a maximum microplastic concentration of approximately 517,000 particles m−2. After a period of severe flooding in winter 2015/16, all sites were resampled. Microplastic concentrations had fallen at 28 sites and 18 saw a decrease of one order of magnitude. The flooding exported approximately 70% of the microplastic load stored on these river beds (equivalent to 0.85 ± 0.27 tonnes or 43 ± 14 billion particles) and eradicated microbead contamination at 7 sites. We conclude that microplastic contamination is efficiently flushed from river catchments during flooding.

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We thank colleagues in the laboratories in the Department of Geography and the School of Earth and Environmental Sciences at The University of Manchester for help with a range of analyses. R.H. was in receipt of a University of Manchester President’s Doctoral Scholar Award, which supported this research. We thank N. Scarle for assistance with the figures and the Environment Agency for discharge data.

Author information


  1. Department of Geography, The University of Manchester, Manchester, UK

    • Rachel Hurley
    • , Jamie Woodward
    •  & James J. Rothwell


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J.W. initiated the microplastics project. R.H., J.W. and J.J.R. conceived and designed the study. R.H., J.W. and J.J.R. conducted the field sampling. R.H. performed all analyses. All authors contributed to interpretation of the data and writing of the manuscript.

Competing interests

The authors declare no competing interests.

Corresponding authors

Correspondence to Rachel Hurley or Jamie Woodward.

Supplementary information

  1. Supplementary Information

    Supplementary data tables and figures

  2. Supplementary data

    Supplementary riverine data