Riverbank macrolitter in the Dutch Rhine–Meuse delta

Abstract

Anthropogenic litter in aquatic ecosystems negatively impacts ecosystems, species and economic activities. Rivers play a key role in transporting land-based waste towards the ocean. A large portion however is retained within river basins, for example in the estuary, in sediments and on the riverbanks. To effectively identify litter sources, sinks and transport mechanisms, reliable data are crucial. Furthermore, such data can support optimizing litter prevention mitigation and clean-up efforts. This paper presents the results of a 2-year monitoring campaign focused on riverbank macrolitter (>0.5 cm) in the Dutch Rhine–Meuse delta. Between 2017 and 2019, volunteers sampled 152 415 litter items at 212 unique locations. All items were categorized based on the River-OSPAR method (based on the OSPAR beach litter guidelines), which includes 110 specific item categories across ten parent categories. The median litter density was 2060 items/km, and the most observed items were foam, hard, and soft plastic fragments (55.8%). Plastic bottles, food wrappings and packaging, caps, lids and cotton swabs were the most abundant specific items. The litter density and most abundant items vary considerably between rivers, along the river, and over time. For both rivers however, the highest litter density values were found at the Belgian (Meuse) and German (Rhine) borders, and at the Biesbosch National Park, the most downstream location. With this paper, we aim to provide a first scientific overview of the abundance, top item categories, and spatiotemporal variation of anthropogenic litter on riverbanks in the Dutch Rhine–Meuse delta. In addition, we evaluate the used River-OSPAR method and provide suggestions for future implementation in (inter)national long-term monitoring strategies. The results can be used by scientists and policy-makers for future litter monitoring, prevention and clean-up strategies.

Disentangling Variability in Riverbank Macrolitter Observations

“…In each round, a pair of volunteers were assigned a specific, predefined location (day of the measurement was chosen by the volunteer, within the four-week window). During each observation, all macrolitter (>2.5 cm) was removed from a 100 m riverbank stretch and categorized according to the River-OSPAR protocol, 7 containing 111 unique item categories (see Figure 2 for a complete list). The microlitter items (between 0.5 and 2.5 cm) were separately obtained and classified by randomly selecting a quadrant of 50 cm × 50 cm on the riverbank and extrapolating the number of items to the whole area (for details, see Van Emmerik et al (2020)).…”

Roadmap litter monitoring in Dutch rivers

“…Monitoring of litter using this method was started in 2017 and is planned to be continued for the coming years. Findings of the riverbank monitoring done by the Schone Rivieren project were recently published(van Emmerik et al, 2020b). These results indicate that plastic bottles, food wrappings and packaging, lids, and cotton swabs are most abundant items on Dutch riverbanks.…”

“…Frequently found items include plastic fragments, food wrappings, caps and lids, as well as cotton swabs (Figure 10, van Emmerik et al, 2020b). 85.1% of the total items found on Dutch riverbanks (n = 152,415) were made of plastic(van Emmerik et al, 2020b). Hotspots were found to be centred around cities (e.g.…”

“…Hotspots were found to be centred around cities (e.g. Maastricht, Nijmegen, Arnhem) and in Biesbosch national Park(van Emmerik et al, 2020b).…”

Routekaart Zwerfafvalmonitoring Nederlandse rivieren

“…(1) 1.3-9.7 kg/dag -0.5-3.5 ton/jaar 16 (2) 16-160 kg/dag -5.8-58 ton/jaar 11 (3) 1,900-6,300 kg/dag -694-2,300 ton/jaar 7 De laagste en hoogste schatting verschillen meer dan drie ordegroottes. (12,13,14) Langetermijnmonitoring.…”