Quantifying uncertainties in visual observations of floating riverine plastic

Abstract

Accurate and reliable monitoring data are crucial for the design of effective reduction and mitigation strategies for riverine macroplastic (>0.5 cm) pollution. One common approach to collect monitoring data is the visual observation method, where floating plastics are counted from bridges to estimate plastic flux. However, this method lacks robust uncertainty analyses, resulting in suboptimal monitoring strategies and unknown error margins. The goal of this study was to quantify these uncertainties and develop a practical workflow to optimize monitoring strategies applicable across different watersheds. Four key design elements that contribute to uncertainty are: cross-sectional coverage, observation time, observation frequency, and recovery. Through a case-study on the Dutch Rhine-Meuse delta we show how these uncertainties can be quantified, and how these insights can be used to optimize a monitoring strategy for a given monitoring goal. By improving the efficiency and effectiveness of monitoring protocols, these insights enhance data quality and reliability, ultimately supporting efforts to mitigate the environmental impacts of macroplastic pollution.

Authors 9

1. Paul Vriend corresponding Aachen Institute of Environmental Sciences (CML)

   Leiden University · Ministry of Infrastructure and Water Management · Rijkswaterstaat

   Affiliation as printed

   Institute of Environmental Sciences, Leiden University, the Netherlands

   Rijkswaterstaat, Ministry of Infrastructure and Water Management, The Hague, the Netherlands

2. Thijs Bosker Aachen Institute of Environmental Sciences (CML)

   Leiden University

   Affiliation as printed

   Institute of Environmental Sciences, Leiden University, the Netherlands

3. Yvette A. M. Mellink

   Wageningen University & Research

   Affiliation as printed

   Aquatic Ecology and Water Quality Group, Wageningen University and Research, Wageningen, the Netherlands

4. Frank P. L. Collas

   Radboud University Nijmegen · Ministry of Infrastructure and Water Management · Rijkswaterstaat

   Affiliation as printed

   Department of Environmental Science, Radboud Institute for Biological and Environmental Science, Radboud University, Nijmegen, The Netherlands

   Rijkswaterstaat, Ministry of Infrastructure and Water Management, The Hague, the Netherlands

5. Felipe Moscoso Cruz
   Affiliation as printed

   Nerdish, Breda, the Netherlands

6. Nadieh Kamp

   Ministry of Infrastructure and Water Management · Rijkswaterstaat

   Affiliation as printed

   Rijkswaterstaat, Ministry of Infrastructure and Water Management, The Hague, the Netherlands

7. Sylvia Drok

   Ministry of Infrastructure and Water Management · Rijkswaterstaat

   Affiliation as printed

   Rijkswaterstaat, Ministry of Infrastructure and Water Management, The Hague, the Netherlands

8. Martina G. Vijver Aachen Institute of Environmental Sciences (CML)

   Leiden University

   Affiliation as printed

   Institute of Environmental Sciences, Leiden University, the Netherlands

9. Tim H. M. van Emmerik corresponding

   Wageningen University & Research

   Affiliation as printed

   Hydrology and Environmental Hydraulics Group, Wageningen University and Research, Wageningen, the Netherlands