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Microplastics pollution in sediments of the Thames and Medway estuaries, UK: Organic matter associations and predominance of polyethylene

Marine Pollution Bulletin 2024 18 citations

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Researchers analyzed microplastic contamination in sediments along the Thames and Medway estuaries in the UK. They found the highest concentrations in urban London, with polyethylene being the most common polymer type, and microplastic abundance was strongly correlated with organic carbon content in the sediment. The study identifies urbanization and combined sewer overflows as key drivers of microplastic accumulation in these estuarine environments.

Study Type Environmental

Microplastics at 10 sites along a 77 km transect of the river Thames estuary (UK) and 5 sites along 29 km of the Medway estuary were separated from sediment and analysed by ATR-FTIR spectroscopy. Microplastics were observed at all sites. Highest Thames concentrations were in urban London between Chelsea and West Thurrock (average 170.80 particles kg-1 ± 46.64, 3.36 mg kg-1 ± 1.79 by mass), mid-outer estuary sites were two to three times lower. Microplastics were slightly dominated by particles (54 %) over fibres (45 %), including polymer types ranked: polyethylene > PET > polypropylene > polyamide. Medway microplastics decreased seaward, with one urban-municipal site impacted by a combined-sewer-overflow containing a high proportion of fibres (Rochester, 484 particles kg-1, 7.39 mg kg-1 by mass). Microplastic abundance was correlated to organic carbon (TOC %) (R2 of 0.71 Thames and 0.96 Medway), but not sediment particle size. Sedimentary microplastics accumulation in the Thames was controlled by urbanisation-distance, and site hydrodynamics.

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