Distribution, Characterization and Risk Assessment of Microplastics in Two Rivers in West Central Scotland: The Black Cart Water and White Cart Water

Improved understanding of the behaviour of microplastics in freshwater systems is important as rivers are major conduits for the transport of particles from land to sea. This study investigated microplastics in two tributaries of the River Clyde, Scotland, UK, that flow through rural, suburban and urban areas. Surface water and sediment were obtained from 25 locations in the Black Cart Water and White Cart Water. Microplastics were isolated and characterized by digital microscopy and ATR-FTIR spectroscopy. Particles were found in four water samples, all from the White Cart. Sediment analysis revealed microplastic abundance ranging from 300 to 600 items/kg in the Black Cart and 33.3 to 567 items/kg in the White Cart. Fragments were the most common particle type and white/transparent the most common particle colour. The most common polymers in the Black Cart were PP > PET > PS > PVC > PTFE and in the White Cart PE > PP > PTFE > PET > PA. Identification of some microplastics was challenging because their FTIR spectra did not correspond well to reference spectra of pure polymers. Although the polymer hazard index at some locations was high due to the presence of particles composed of PVC and PA, the ecological risk from microplastics in the Cart river system was generally low.