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

• Published in: Marine pollution bulletin Vol. 208; p. 116971
• Main Authors: Trusler, Megan M., Moss-Hayes, Vicky L., Cook, Sarah, Lomax, Barry H., Vane, Christopher H.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-11-2024
• Subjects: Estuary; London; Microplastic pollution; Particle-size; Plastic polymer; Tideway; Tideway; London; Particle-size; Microplastic pollution; Estuary; Plastic polymer
• ISSN: 0025-326X; 1879-3363; 1879-3363
• DOI: 10.1016/j.marpolbul.2024.116971

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.
•First longitudinal survey of microplastics in sediments Thames and Medway estuaries•Polyethylene dominant over PET, polypropylene and polyamide•Microplastics abundance corresponds with a seaward decline in organic carbon.•Microplastics accumulation in Thames and Medway influenced by meander flow•Microplastics elevated close to combined sewer overflow discharges points