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Assessment of riverine litter (plastics) inputs to the marine environment

Periodic Reporting for period 1 - LitRivus (Assessment of riverine litter (plastics) inputs to the marine environment)

Reporting period: 2020-04-01 to 2022-03-31

Marine litter is a major global environmental concern and highly relevant in the political agendas and environmental policy frameworks. A large amount of plastics enters the ocean every year from land-based sources (considered the major contributor to marine litter), causing negative impacts to the marine environment and loss of ecosystem services. Global input of plastics via rivers, connecting inland generated waste to the marine environment, has been estimated as a major contributor. However, field data are very scarce and lacking temporal resolution. This is a key issue that can lead to significant uncertainties in riverine litter fluxes; identification of hotspots and implementation of mitigation measures may not be appropriately targeted.

Showing the magnitude of the problem, not only in the marine environment, but also at the sources, is essential for society. Describing how anthropogenic waste can be emitted to the environment, polluting freshwaters, and eventually reaching the ocean via rivers, can help in bringing the societal and political changes needed to abate plastic pollution. The observed limitations in managing plastic waste, whether in high-income or low-income economies, calls for the implementation of mitigation strategies oriented towards reducing plastic consumption and avoiding waste generation. LitRivus plays an important role in informing our society that plastic pollution is not only an overseas issue, but also at European scale.

LitRivus can greatly advance the field of marine litter and the global plastic’s issue. The Action focused on innovative monitoring methods to study riverine litter input. Empirical data facilitate formulation of models to reduce uncertainties and improve estimations. Moreover, the use of international data and collaboration with EU and non-EU scientists provides the project a large scale. Publication of LitRivus’ results serves larger goals pursued by the scientific community, e.g. calculation of marine litter mass balances at different geographical and temporal scales. Furthermore, this the first-time comprehensive data on riverine litter inputs will be evaluated in relation to policy and decision-making frameworks, such as the Marine Strategy Framework Directive, Water Framework Directive and the EU Strategy for plastics, thus guaranteeing that science-policy knowledge transfer is achieved in order to improve plastic mitigation measures.
Considering existing data/knowledge gaps, the following work has been performed:

- Field monitoring has been used to identify dynamics of micro/meso/macro litter of riverine inputs to the marine environment. New tools and methods have been used for monitoring of riverine litter inputs, collecting more than two hundred samples of microplastics and forty-eight samples of macroplastics. The different results obtained from field monitoring have been presented at international conferences, and a final joint scientific publication is being prepared.

- LitRivus performed an assessment of riverine litter inputs to the marine environment at a large scale (EU scale) entitled ‘Floating macrolitter leaked from Europe into the ocean’. The collaborative monitoring of 42 rivers in 11 countries across Europe provided the largest database of riverine floating macrolitter input to the ocean. The team behind this study, led by Daniel González-Fernández and Andrés Cózar ( was composed of 22 institutions from 12 countries.

- This action included a secondment at the DG Joint Research Centre (JRC) of the European Commission, under the supervision of Dr. Georg Hanke. LitRivus initiated the qualitative analysis of the Monitoring Programmes and Programmes of Measures delivered by EU Member States for the implementation of the Marine Strategy Framework Directive (MSFD), focusing on the role of riverine litter at EU level. During the Secondment, the JRC agreed that this activity should be postponed matching with the timeline of the tasks planned by the ‘MSFD Marine Litter Technical Group’ (TG ML) for 2022 and 2023. This has resulted in a long-term collaboration between the University of Cádiz and the JRC. Daniel González-Fernández is invited regularly as an expert on floating litter and riverine litter to the TG ML meetings.

- Multiple international collaborations have led to several scientific publications and organization of special issues in international journals, dissemination of results and convening of sessions at international scientific conferences, and science-policy interactions in meetings organized by the European Commission (i.e. TG ML meetings). The methodologies employed by LitRivus have been shared with interested scientific institutions and NGO’s beyond EU (e.g. Turkey, Vietnam, South Africa and Brazil). In terms of public engagement and awareness, LitRivus has participated in communication activities such as press releases, social media, webinars, seminars, workshops, outreaching to non-scientific audiences.
Results from field monitoring have shown differences in plastic concentrations between floating, suspended, and bottom samples. Floating plastics showed the highest concentrations. However, given the variability in water depth across the rivers, suspended plastics may provide a major loading of plastics to the ocean. In estuarine environments, there can be differences in plastic concentration due to the action of tides, i.e. spring tides are associated to higher concentrations. In general, correlation between plastic concentration and river flow is low, hindering temporal extrapolations to calculate annual loadings. Monitoring data provides new information on plastics distribution, variability and dynamics in rivers that will be exploitable through their incorporation in further modelling exercises. Such results and new model outputs will provide input to policy-makers to identify hotspots and evaluate the potential effectiveness of mitigation measures.

The study entitled ‘Floating macrolitter leaked from Europe into the ocean’, published in Nature Sustainability journal, revealed that high-income economies are among the top contributors to plastic litter emitted from Europe to the ocean. Most of the land-sourced plastic is routed through numerous small rivers, streams, and surface run-off along populated coasts. This brings a whole new scenario for policy-makers, since previous models had only focused on a limited number of large rivers as major contributors to the marine litter issue. LitRivus’ results demonstrate that, at European scale, floating macrolitter loading is scattered through a myriad of land-based inputs along the coasts, presenting a more complex scenario for the interception and capture of plastic entering the ocean than previously thought. The impact of this publication goes beyond the scientific community and has become a science-policy tool for the European Commission.

The initial assessment of the Monitoring Programmes and Programmes of Measures against plastic pollution in relation to riverine litter at EU level revealed a series of issues: a major lack of coordination between coastal and river basin regulations regarding monitoring of riverine and marine litter; the need for an early alignment of methods across different marine basins; and the potential need for a pan-European workshop on riverine litter monitoring methodologies.