Microplastics pollution in sediments of the Thames and Medway estuaries, UK: Organic matter associations and predominance of polyethylene
Megan M. Trusler, Vicky Moss‐Hayes, Sarah Cook, Barry H. Lomax, Christopher H. Vane
Abstract
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 %) (R 2 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