Abstract
Microplastics (MP) are transported from land-based sources from rivers to marine waters. However, there is currently little knowledge about MP fate from land sources to marine waters. Traffic is estimated to be one of the largest sources of MP; hence, stormwater is expected to be an important transportation route of MP to marine waters. The aim of this study was to investigate the effect of the size and density of tyre wear particles in road run-off on their fate in the Göta River in Sweden using hydrodynamic modelling. The model of the stretch of Göta River, Sweden’s largest river, passing through Gothenburg (Sweden’s second largest city) and out to the sea, was set up using MIKE 3 FM software. Literature data were used to define the MP characteristics: concentrations in stormwater, prevalent particle sizes, density of MP commonly occurring in road run-off and settling velocities. Results show that higher concentrations of MP are found on the south side of the river, compared with the north side, due to higher annual average daily traffic loads along the south side of the river. The mixing processes in the river and the MP concentrations were generally influenced by the vertical water density gradient caused by saline water from the Kattegat strait. While most MP with higher density and larger size settle in the river, smaller MP with density close to 1.0 g/cm3 do not settle in the river and therefore reach the Kattegat strait and the marine environments. Further research is needed to describe the fate and transport of microplastics in the stormwater system, including treatment facilities, i.e. biofouling, aggregation, degradation and/or further fragmentation and settling.
Highlights
Plastic pollution is present in most bodies of water on the planet; this has become one of our most seriousResponsible editor: Philippe Garrigues Electronic supplementary material The online version of this article contains supplementary material, which is available to authorized users.Environ Sci Pollut Res (2020) 27:24218–24230(Baldwin et al 2016; Hong et al 2017; Anderson et al 2016; Rocha-Santos and Duarte 2015)
Traffic-related stormwater is expected to be a major transportation route of MP into receiving freshwater bodies and subsequently into marine waters (Siegfried et al 2017), little is known about the fate and transport of MP in general, and of traffic-related MP in particular, in rivers; and this study aims to fill some of the knowledge gap
The aim of this study was to investigate the effect of the size and density of tyre wear particles in road run-off on their fate in the Göta River in Sweden using hydrodynamic modelling
Summary
It is estimated that 10% of the annual production of plastics (approximately 350 t in 2014 [Auta et al 2017; Boucher and Friot 2017]) ends up in our oceans and that 70–80% of marine MP originate from land-based sources, transported mainly via rivers (Horton et al 2017a, b). Tyre debris is identified as a major source of MP in marine environments: 28% of the global release of MP to oceans is assumed to be released from tyres (Boucher and Friot 2017). Tyre rubber contains several chemicals of environmental concern, such as PAH and Zn, and leachate from tyre particles has shown ecotoxicological effects on aquatic organisms (Wik and Dave 2009; Capolupo et al 2020)
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