Monitoring Plastics in Rivers and Lakes: Guidelines for the Harmonization of Methodologies

Executive summary
More than 8,000 million metric tons of plastics have been made since the beginning of large-scale production in the 1950s. As a consequence of the omnipresence of plastic products, combined with insufficient waste management and handling practices, plastic debris has entered the environment and is present in practically all ecosystems. It has been detected even in remote locations such as mountain lakes and polar sea ice. The most prominent example of widespread plastic contamination of the environment is provided by the world’s oceans. Research, societal awareness and actions have long focused on marine plastics.

Based on our current knowledge, the vast majority of marine plastics originate from land-based sources. Hence, the focus of research as well as actions has been expanded to freshwater and terrestrial environments. Rivers have been identified as major pathways for connecting land-sourced plastics with marine environments. Moreover, rivers and other freshwater bodies such as lakes and reservoirs are themselves threatened by plastics contamination in the same way as the marine environment.

Despite its relevance and a growing body of data and knowledge on freshwater plastics, the current understanding of transport processes, loads and impacts is limited, mainly because data are lacking. Most published data on freshwater plastics stem from individual projects which apply different sampling and analysis techniques. This lack of harmonization hampers the comparison and ultimately the synthesis of data.

This report builds on the large body of knowledge and experience gained from marine plastic monitoring. For example, methods of sample processing and instrumental analytics for particle characterization are mostly the same for freshwater and marine systems. Many other aspects require the adaptation of sampling techniques and the design of monitoring programmes according to specific freshwater conditions, such as the typically high content of coarse natural particulate material or the high variability of plastic concentrations in rivers driven by river flow variations.

The report provides methodological guidelines to support monitoring and assessment programmes for plastics in freshwater. It contains the most current procedures for monitoring and analysing plastic content in rivers, lakes, reservoirs and water/wastewater treatment plants.

Recommendations have been developed reflecting stakeholder inputs from a series of workshops, which revealed that developing and developed countries face similar challenges with the implementation of monitoring programmes for plastics in freshwater environments. However, the type and intensity of hurdles to be overcome in setting up monitoring programmes may differ in different countries. The guidelines are designed to assist in the timely development and implementation of freshwater plastic monitoring programmes, tailored to the different starting conditions in the different countries.

Such monitoring programmes are needed in order to prioritize land-based sources, which is a prerequisite for achieving United Nations Sustainable Development Goal 14, Target 14.1 to “prevent and significantly reduce marine pollution of all kinds, particularly from land-based activities, including marine debris and nutrient pollution” by 2025 (

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United Nations Environmental Programme

June 21, 2021
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