Assessing riverine litter input variability to the marine environment at large scale through field data collection: progress in marine litter pollution science beyond the state-of-the-art.

Marine litter is a major global environmental concern and highly relevant in the political agendas and environmental policy frameworks, including the UN Sustainable Development Goals.The fact that the patterns in dynamics and distribution of riverine litter remain unknown to date underlines that LitRivus can greatly advance the field of marine litter and the global plastics issue. The project will be focused on innovative monitoring methods to study riverine litter input, providing details on dynamics and variability of litter flux in rivers, which is the missing information necessary to validate models for assessment of riverine litter loads to the sea. Empirical data will facilitate formulation of models to reduce uncertainties and improve estimations. Moreover, the use of international data from RIMMEL project (DG Joint Research Centre, European Commission) and collaboration with experts will provide the project a large scale. Publication of these results will be very welcome internationally, providing a new approach to the topic based on field data, and serving larger goals pursued by the scientific community, e.g. calculation of marine litter mass balances at different geographical and temporal scales. Furthermore, this will be 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.

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. A compilation of field data collected by LitRivus is being prepared for a scientific publication.

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. A Press Release and a free copy of the article are accessible at our website. 

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.