Potentially toxic metals, anthropogenic microfibres and other microplastics in sediments from a small, urban estuary (Plym, southwest England)

Anthropogenic microfibres (AMFs) and microplastics (MPs) are pervasive and ubiquitous environmental contaminants of growing concern. However, their study in geosolids, like sediments, is often conducted in the absence of other important geochemical and anthropogenic markers. In the present study, surface and subsurface sediments from the Plym Estuary, southwest England, have been analysed for AMFs and MPs along with organic matter (as loss on ignition; LOI), calcium, iron, manganese and potentially toxic metals (PTMs). The latter were heterogeneously distributed throughout the estuary because of multiple inputs and variations in sediment granulometry. AMFs were mainly constructed of cellulosic and petroleum-based polymers and concentrations correlated with LOI and certain PTMs. However, AMFs exhibited a clear peak (2800 and 11,200 kg⁻¹ for surface and subsurface sediments, respectively) in the vicinity of a wastewater treatment plant, with evidence of a more diffuse, atmospheric input throughout the system. Other, less commonly observed MPs, consisted of petroleum-based fragments. With less favourable aerodynamic characteristics for atmospheric transport and a correlation with Ca, it is suggested that an offshore source might be significant. The decoupling of fibres and fragments by source and transport is a more general phenomenon identified for further study.