Rapid assessment of floating macroplastic transport in the Rhine

Abstract

<p>Most marine litter pollution is assumed to originate from land-based sources, entering the marine environment through rivers. To better understand and quantify the risk that plastic pollution poses on aquatic ecosystems, and to develop effective prevention and mitigation methods, a better understanding of riverine plastic transport is needed. To achieve this, quantification of riverine plastic transport is crucial. Here, we demonstrate how established methods can be combined to provide a rapid and cost-effective characterization and quantification of floating macroplastic transport in the River Rhine We combine visual observations with passive sampling to arrive at a first-order estimate of macroplastic transport, both in number (10 - 75 items per hour) and mass per unit of time (1.3 – 9.7 kg per day). Additionally, our assessment gives insight in the most abundant macroplastic polymer types the downstream reach of the River Rhine. Furthermore, we explore the spatial and temporal variation of plastic transport within the river, and discuss the benefits and drawbacks of current sampling methods. Finally, we present an outlook for future monitoring of major rivers, including several suggestions on how to expand the rapid assessment presented in this paper.</p>

Effects of hydrodynamics on the cross‐sectional distribution and transport of plastic in an urban coastal river

“…van Emmerik, Strady, et al (2019) sampled macroplastics (>5 cm) from the surface to 1–1.3 m depth in the Saigon River of Vietnam and found 88%–90% of plastics in the upper 0.5 m. In Jakarta (Indonesia), van Emmerik, Loozen, van Oeveren, Buschman, and Prinsen (2019) reported macroplastic (>1.5 cm) concentrations that were on average five times higher in the uppermost 0.425 m of the river than between 0.425 and 1 m deep. For the lateral distribution of floating macroplastics across river widths, van Emmerik, Loozen, et al (2019) observed plastics concentrated in the center in mostly channelized and straight rivers of Jakarta, but other studies showed more horizontal variability (van Emmerik, Loozen, et al, 2019; van Emmerik, Tramoy, et al, 2019; Vriend et al., 2020); they suggest that in addition to flow velocities, distributions may be affected by flow and tidal dynamics, wind directions and speed, river geometries, and navigation activities. van Calcar and van Emmerik (2019) synthesized the literature on surface macroplastic transport for over 20 rivers, showing different spatial variability patterns of plastic across river widths, ranging from the majority of plastic concentrated in the center or at side sections to cases with almost equal cross‐sectional distributions.…”

Roadmap litter monitoring in Dutch rivers

“…Several studies have been published on floating riverine litter transport in the Dutch Rhine delta. Estimates of plastic exports by Dutch rivers range between 1.3 -6300 kg per day (Vriend et al, 2020b, van der Wal et al, 2015Lebreton et al, 2017). Tauw) to determine plastic transport.…”

“…Floating litter concentrations in these cities were found to be 111-133 items per kilometre of canal, with pollution hotspots around more populous areas within the cities. (Vriend et al, 2020b).…”

Macroplastic Storage and Remobilization in Rivers

“…In future works, more details may be determined using a combination of a visual counting method with hydrodynamic modelling [57]. Insight into macroplastic transport distance may be also gained by modifications of the existing hydrodynamic models used for simulations of the transport of large woody debris [e.g., 44,58] as well as by long-term observations of plastic accumulation on riverbanks [59].…”

“…Previous works on surface and subsurface storage of macroplastic debris used hand collection and sieve analysis for estimation of plastic abundance (Table 1). Analysed samples were collected from quadrats [30,34,62,63], circles [64] or transects [65] delimited parallel or perpendicular to the shoreline of river channel or reservoir [59]. Obtained results were usually described as number of plastic debris items or their mass per surface area (m 2 ) of sampled plot (Table 1), which is useful for estimation of plastic abundance in contemporary surface sediments, but does not allow for reliable comparison with volumetric samples of sediments taken from cores or river banks.…”