title: Fate of nano- and microplastic in freshwater systems: A modeling study.
abstract: Riverine transport to the marine environment is an important pathway for microplastic. However, information on fate and transport of nano- and microplastic in freshwater systems is lacking. Here we present scenario studies on the fate and transport of nano-to millimetre sized spherical particles like microbeads (100 nm-10 mm) with a state of the art spatiotemporally resolved hydrological model. The model accounts for advective transport, homo- and heteroaggregation, sedimentation-resuspension, polymer degradation, presence of biofilm and burial. Literature data were used to parameterize the model and additionally the attachment efficiency for heteroaggregation was determined experimentally. The attachment efficiency ranged from 0.004 to 0.2 for 70 nm and 1050 nm polystyrene particles aggregating with kaolin or bentonite clays in natural freshwater. Modeled effects of polymer density (1-1.5 kg/L) and biofilm formation were not large, due to the fact that variations in polymer density are largely overwhelmed by excess mass of suspended solids that form heteroaggregates with microplastic. Particle size had a dramatic effect on the modeled fate and retention of microplastic and on the positioning of the accumulation hot spots in the sediment along the river. Remarkably, retention was lowest (18-25%) for intermediate sized particles of about 5 μm, which implies that the smaller submicron particles as well as larger micro- and millimetre sized plastic are preferentially retained. Our results suggest that river hydrodynamics affect microplastic size distributions with profound implications for emissions to marine systems.
authors.affiliation: Aquatic Ecology and Water Quality Management Group, Wageningen University & Research, P.O. Box 47, 6700 AA Wageningen, The Netherlands; Wageningen Marine Research, P.O. Box 68, 1970 AB IJmuiden, The Netherlands. Electronic address: ellen.besseling@wur.nl.
authors.forename: Ellen
authors.initials: E
authors.lastname: Besseling
authors.affiliation: Aquatic Ecology and Water Quality Management Group, Wageningen University & Research, P.O. Box 47, 6700 AA Wageningen, The Netherlands; National Institute for Public Health and the Environment (RIVM-DMG), P.O. Box 1, 3720 BA Bilthoven, The Netherlands.
authors.forename: Joris T K
authors.initials: JTK
authors.lastname: Quik
authors.affiliation: Aquatic Ecology and Water Quality Management Group, Wageningen University & Research, P.O. Box 47, 6700 AA Wageningen, The Netherlands.
authors.forename: Muzhi
authors.initials: M
authors.lastname: Sun
authors.affiliation: Aquatic Ecology and Water Quality Management Group, Wageningen University & Research, P.O. Box 47, 6700 AA Wageningen, The Netherlands; Wageningen Marine Research, P.O. Box 68, 1970 AB IJmuiden, The Netherlands.
authors.forename: Albert A
authors.initials: AA
authors.lastname: Koelmans
mesh_terms: D005618:Fresh Water / Q000737:chemistry; D019015:Geologic Sediments; D057446:Hydrodynamics; D008962:Models, Theoretical; D049329:Nanostructures / Q000032:analysis*; D010316:Particle Size; D010969:Plastics / Q000032:analysis*; D011108:Polymers / Q000032:analysis; D011137:Polystyrenes / Q000032:analysis*; D045483:Rivers / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D010969:Plastics; D011108:Polymers; D011137:Polystyrenes; D014874:Water Pollutants, Chemical
keywords: Fate modeling; Freshwater; Microplastic; Nanoplastic; Particle transport; Sedimentation