Microplastics and other plastic-like microdebris in sediments from the Dart River and Estuary, southwest England

Abstract

Surficial sediment samples (n = 10) collected from a transect of a river-estuary (Dart) in southwest England have been analysed for geochemical characteristics, anthropogenic metals (Cr, Cu, Sn, Pb, Zn), and microplastics (∼50 μm–5 mm) and other microplastic-like debris. Results indicated the finest grains towards the lower river and upper estuary, a seaward increase in sedimentary Ca, and loss on ignition ranging from about 0.7 to 4 %. Anthropogenic metals were heterogeneously distributed throughout the catchment with maximum concentrations in the river or lower estuary. Microplastics were dominated by fibres, with concentrations ranging from 110 to 1800 kg⁻¹ and composition either cellulosic (cotton or rayon) or thermoplastic (polyester or acrylic). Microfibre abundance exhibited no clear relationships with geochemical characteristics or anthropogenic metals but fibres were enriched downstream of a wastewater treatment plant and accumulation of larger fibres was greatest where sediments were finest. Other microdebris was observed in four samples and consisted of fragments (mainly paint flakes) and hollow glass beads. Paint flakes identified as antifouling formulations enriched in Cu, Zn and Sn and road markings containing solid glass beads. Maximum sediment Cu and Zn concentrations coincided with the location where the majority of paint flakes (>2000 kg⁻¹) were encountered. While not all microscopic particles identified in the present study are plastic, they share similar properties and likely have common impacts. Accordingly, and more generally, we recommend that a broader array of both plastics and plastic-like particles, coupled with measures of sediment geochemistry and anthropogenic impact, are considered in environmental studies and impact assessments.