Microplastics in sediments of the River Thames Basin, UK

The average percentage effluent present in the river was estimated using the Low Flows 2000 (LF2000) WQX (Water Quality eXtension) model. The population equivalent density was calculated using population within the catchment area (of known area) served by the upstream sewage treatment works. This site characteristic data is given in the datasheet

ThamesMicroplastics_SamplingLocations.
Four replicate sediment samples were taken at each site using a stainless steel scoop, collected into a 1 L glass jar. In the laboratory the 1 L sediment samples were wet-sieved and sediment in the size ranges 1-2 mm and 2-4 mm was retained for further analysis. Microplastic particles were extracted using a number of steps, consisting of manual sorting and density separation with zinc chloride solution (1.7-1.8 kg/L). Each sample comprised a different volume and weight following size-sieving, therefore the inclusion of dry weight data allows for the conversion of total microplastic particles into a concentration (e.g. particles/kg dry sediment) for comparability between samples (ThamesMicroplastics_NumberOfParticles).

A subsample (20%) of particles were characterised by type and colour, with composition determined using Raman spectroscopy (ThamesMicroplastics_ParticleCharacteristics). Further details on the methods used for particle extraction and characterisation are available in the supporting information.