Microplastic Pollution in Sediment Cores from the River Thames UK

Abstract

Microplastics are ubiquitous contemporary pollutants due to their pervasive nature. Sediments from four sites along the River Thames were collected for microplastic extractions. Microplastics were extracted, counted under a microscope, and classified as fibres, fragments, and microbeads. They were then analysed by FTIR-ATR, and carbon isotopic signatures were studied. Microplastics were found at all four sites. The highest average microplastic concentration was observed at Millennium Bridge (N=6), with an average of 2229 particle Kg-1 ± 1026, followed by Battersea Bridge (N=4), with an average of 2165 particle Kg-1 ± 1069 and Gallions Reach (N=3) with an average of 850 particle Kg-1 ± 946. The lowest concentration was found at Mucking Flat (N=3) with an average of 512 particle Kg-1 ± 262. Twenty-one potential microplastic particles were analysed by FTIR. 52 % were identified as polycarbonate, 24 % as non-microplastics, 19 % as High-Density Polyethylene (HDPE), and 5 % as Chlorinated Polyethylene. The isotope analysis shows a mixture of fuel and plant-based plastic origin across sites, with Gallions Reach exhibiting the widest isotopic range with variation in C wt %. Microplastic concentration was correlated with the distance from the urban source. A correlation was observed between lead concentration (Pb / 208 mg/kg) and the mean of microplastics in particle/kg at different depth intervals across various sites. In contrast, a moderate correlation was found between sample depth and Cw%. Possible factors influencing the microplastic concentration are urbanisation and the inefficiency of water treatment plants in detecting and eliminating microplastics effectively.